Infectious diseases of the skin Flashcards

Question

25- A goat farmer presents with fever and flu-like symptoms, as well as violaceous papulonodules on the trunk and lower extremities. You consider Malta fever in your differential diagnosis. Which of the following statements regarding this diagnosis is correct? A. Treatment is with doxycycline B. Treatment is with ciprofloxacin C. Skin lesions are frequently seen D. Caused by a gram positive rod E. Occurs frequently in the US

Answer 1

Correct choice: A. Treatment is with doxycycline Explanation: Treatment of malta fever is with doxycycline or rifampin. Malta fever is another name for Brucellosis. This infection is caused by ingesting raw goat milk and unpasteurized goat cheese infected with Brucellae (gram-negative rods). It is infrequent in the US, occurring mainly in veterinarians and farmers. Acute brucellosis has very non-specific features and presents as a flu-like illness. Skin lesions are infrequent (20% of cases) but are usually violaceous papulonodules on the trunk and lower extremities.

Answer 2

Correct choice: E. Ingestion of unpasteurized dairy products Explanation: Brucellosis (aka Undulant fever; Malta fever) is caused by the gram-negative bacterium Brucella spp. It is typically contracted via direct contact with an infected animal (undulant) or ingestion of infected meat or unpastuerized dairy products. Butchers, farmers, veterinarians, and unwise tourists are at highest risk. Clinical findings include: cyclic fevers, arthralgias, hepatosplenomegaly, rare skin involvement with a violaceous papulonodular eruption, and/or endocarditis (most common cause of death). The treatment of choice is doxycycline combined with rifampin. The remaining answer choices have the following disease associations: Contact with rabbits-Tularemia, Ingestion of raw seafood- Vibrio infection, Flea bite from infected animal- Plague ,Inhalation of aerosolized bird excretions- Psittacosis.

Answer 3

Correct choice: B. Doxcycyline Explanation: Secondary syphillis is caused by the spirochete, T. pallidum. Penicillin is the treatment of choice for secondary syphillis. In penicillin allergic individuals, doxycyline may be used. Treatment for neurosyphilis, congenital syphilis and syphilis in pregnant women is desensitization to penicillin and then treatment with pcn.

Answer 4

Correct choice: D. Pseudomonas aeruginosa Explanation: Hot tube folliculitis is due to Pseudomonas aeruginosa in the setting of use of a hot tub/whirlpool 12-48 hours prior to onset. It is characterized by edematous, pik to red follicular papules and pustules, primarily on the trunk. It is often pruritic and resolve sspontaneously in immunocompetent hosts. It my be a serious illness in immunocompromised hosts. The condition is generally self-limited - patients can use antibacterial soap. If severe or immunocompromised, patient can take ciprofloxacin for 7-14 days. The water in the hot tub, whirpool or swimming pool must be maintained with chlorine and changed every 6-8 weeks to lower organic carbon level.

Answer 5

Correct choice: A. Pox virus Explanation: This is molluscum contagiosum which is due to a pox virus.

Answer 6

Correct choice: B. Scytalidium dimidiatum Explanation: Scytalidium dimidiatum is a non-dermatophyte cause of tinea pedis that is very difficult to treat due to its resistance to most antifungals. It is sensitive to cylcoheximide so it should be cultured on media free of this antifungal.

Answer 7

Correct choice: B. Clarithromycin Explanation: This patient most likely has contract Mycobacterium marinum, otherwise known as "fish tank granuloma." A reasonable approach to treatment of M. marinum consists of treatment with two antibiotics for one to two months after resolution of symptoms. One approach consists of clarithromycin combined with ethambutol OR rifampin. For minimal disease, some favor single- drug therapy with clarithromycin, minocycline or doxycline. The other antibiotic choices are not considered first-line for single-drug therapy.

Answer 8

Correct choice: A. Apple jelly Explanation: Leishmaniasis recidivans is a type of Old World leishmaniasis. Clinically, it appears as a red papule covered with white scale. On diascopy, it has a characteristic apple jelly color. The other listed colors are not seen on diascopy of leishmaniasis.

Answer 9

Correct choice: B. T. tonsurans Explanation: T. tonsurans is currently the primary cause of tinea capitis in the US. None of the remaining listed answers is the most common current cause of tinea capitis (M. audouinii was previously the primary cause of tinea capitis in the US).

Answer 10

Correct choice: A. Interleukin 2 Explanation: The lesion is high immune or tuberculoid leprosy, which is associated with Th1 cytokines including IFN-gamma, IL2, IL12, IL15, IL18 and IL23. Lepromatous leprosy is associated with Th2 cytokines including IL4, 5, 10 and 13.

Answer 11

Correct choice: A. Kytococcus sedentarius Explanation: Pitted keratolysis is a skin disorder characterized by crateriform pitting that primarily affects the pressure-bearing aspects of the plantar surface of the feet. It is caused by a cutaneous infection with micrococcus sedentarius which is included in the Corynebacteria genus. These are gram-positive, catalase-positive, aerobic or facultatively anaerobic, generally nonmotile rods. Corynebacterium diphtheriae infection is classically characterized by a local inflammation, usually in the upper respiratory tract, associated with toxin-mediated cardiac and neural disease. Corynebacterium tenuis causes trichomycosis Patients typically present with yellow, black, or red pinpoint nodules on the hair shafts in the inguinal region. Staphylococcus aureus is a common bacterium that can result in formation of pustules, furuncles, cellulitis and abscesses. Candida species are responsible for superficial infections such as oropharyngeal candidiasis (thrush) and vulvovaginal candidiasis (vaginal Candidiasis) and is also occurs as an opportunistic infection The other associated organisms do not cause pitted keratolysis.

Answer 12

Correct choice: C. Corynebacterium tenuis Explanation: Corynebacterium tenuis is the causative organism associated with most cases. Although up to 33% of adults have colonization by this bacterium in the inguinal or axillary regions, factors such as hyperhidrosis predispose to more extensive growth and resultant clinical manifestations. The other answer choices listed are incorrect.

Answer 13

Correct choice: D. M. ulcerans Explanation: The image depicts a Buruli ulcer, which is due to infection with Mycobacterium ulcerans. Buruli ulcer is a neglected tropical disease of skin and subcutaneous tissue that can result in long-term cosmetic and functional disability. It is a geographically restricted infection but transmission has been reported in endemic areas in more than 30 countries worldwide. The heaviest burden of disease lies in West and Sub-Saharan Africa where it affects children and adults in subsistence agricultural communities. Mycobacterium ulcerans infection is probably acquired via inoculation of the skin either directly from the environment or indirectly via insect bites. The environmental reservoir and exact route of transmission are not completely understood. Treatments include excision, local heating (as mycobacteria prefer cooler temperatures); drug therapy is often disappointing. The other mycobacteria are not the most common cause of a Buruli ulcer.

Answer 14

Correct choice: C. Diagnosis may be made by sending a sample for real-time PCR assay to the Centers for Disease Control and Prevention. Explanation: This is cutaneous leishmaniasis. Amastagotes are seen in dermal macrophages. Leishmaniais grows on Nicolle-Novy-MacNeal media or chick embryo media. The CDC does complimentary diagnoses for leishmaniasis with PCR. Old World cutaneous leishmaniasis and New World leishmaniasis typically resolves without treatment, but is treated to minimize scarring and prevent dissemination. The treatment of choice is parenteral pentavalent antimonials for cutaneous and mucocutaneous forms, while liposomal amphotericine B is used for visceral leishmaniasis. Leishmaniasis organisms often line up at periphery of vacuole without forming any surrounding pseudocapsules in contrast to histoplasma infection with evenly spaced organisms, that are surrounded by a pseudocapsule.

Answer 15

Correct choice: E. Ciprofloxacin Explanation: Oroya Fever (Carrion's Disease) is caused by Bartonella bacilliformis. The Lutzomyia sandly is the vector. Multiple antimicrobial agents are active against B. bacilliformis in vitro, including fluoroquinolones, chloramphenicol, doxycycline, and rifampin. Ciprofloxacin is a reasonable first-line treatment, although resistance is increasing. Therefore, many favor a combination of ciprofloxacin and ceftriaxone. Previously, chloramphenicol was the preferred agent, as it has activity against Salmonella as well, a common secondary infection. However, treatment failure has been described with chloramphenicol. In addition treatment of Oroya fever with chloramphenicol does not eliminate risk for development of verruga peruana. The other answer choices are not the current choice of antibiotics for Oroya Fever.

Answer 16

Correct choice: D. Trichodysplasia spinulosa-associated polyoma virus (TSPyV) Explanation: She has trichodysplasia spinulosa which is seen in settings of immunosuppression. Recently, TSV has been identified as the causative agent.

Answer 17

Correct choice: B. Bullous impetigo Explanation: Bullous impetigo is caused by phage group II Staphylococcus aureus. This question tests the examinee’s knowledge of bacterial infections and in particular those caused by S. aureus. Of the answer choices, bullous impetigo (choice 2) is most closely associated with S. aureus infection. In bullous impetigo, phage group II S. aureus produces exfoliatoxins A/B which cleave desmoglein 1, leading to bulla formation. In contrast to acute paronychia, which is commonly caused by S. aureus, chronic paronychia (choice 1) is related more to chronic irritant/allergic contact dermatitis than infection. Most cases of cellulitis (choice 3), bullous or otherwise, are not cultured, but it is generally considered to be caused more often by streptococci than staphylococci. Blistering distal dactylitis (choice 4) and ecthyma (choice 5) are most commonly caused by Streptococcus pyogenes.

Answer 18

Correct choice: A. Corynebacterium minutissimum Explanation: Choice 1, corynebacterium minutissimum, is the causative agent in erythrasma, which is the described condition. Coral-red fluorescence with Wood’s light is attributable to coproporphyrin III, produced by the bacterium. Trichophyton rubrum is a dermatophyte, which would respond well to topical terbinafine. Malassezia furfur is the yeast implicated in Pityriasis Versicolor. Kytococcus sedentarius is a bacterium which is often associated with pitted keratolysis.

Answer 19

Correct choice: A. HIV status Explanation: Molluscum contagiosum can occur in the setting of immunodeficiency, including in patients with HIV or following treatment with immunosuppressive drugs. In immunocompromised patients, lesions can be large and widespread. Since the introduction of potent antiretroviral therapy, the number of molluscum cases in HIV patients has decreased substantially. Patient with extensive lesions should be tested for HIV infection and the possibility of other immune system disorders also can be considered. The other conditions are not as strongly associated with large, disseminated molluscum lesions.

Answer 20

Correct choice: A. Normal flora Explanation:Superficial folliculitis is characterized by follicular pustules, often arising on an erythematous base. It favors areas with terminal hairs, such as the scalp and beard, as well as the upper trunk, buttocks, and lower extremities. Bacterial culture of pustular contents most commonly reveals normal flora, followed by Staphylococcus aureus.

Answer 21

Correct choice: C. Desmoglein 1 Explanation: In staphylococcal scalded skin syndrome (SSSS), phage group II Staphyloccocus aureus produces toxins that cleave desmoglein 1. This question presents the examinee with an image depicting the highly characteristic periorificial radial crusting and fissuring of SSSS, and assesses knowledge of disease pathomechanism. In SSSS, phage group II Staphyloccocus aureus produces exfoliatoxins (epidermolytic toxins) A and B, which disseminate hematogenously to cleave desmoglein 1 (choice 3), leading to desmosomal splitting, granular layer disruption, and formation of superficial bullae. Desmoplakin (choice 1) is mutated in Carvajal syndrome, which consists of striate palmoplantar keratoderma, woolly hair, and left-sided cardiomyopathy. Desmocollin 1 (choice 2) is the target antigen in the subcorneal pustular dermatosis type of IgA pemphigus. Autoantibodies to desmoglein 3 (choice 4) are formed in pemphigus vulgaris. Mutations in desmoglein 4 (choice 5) occur in autosomal recessive monilethrix and localized autosomal recessive hypotrichosis.

Answer 22

Correct choice: E. Potassium hydroxide preparation Explanation: A potassium hydroxide (KOH) preparation should be performed to diagnose tinea manuum/pedis presenting as the “two feet-one hand syndrome.” This question requires the examinee to identify the “two feet-one hand syndrome” of tinea manuum/ pedis. In the photo only the left hand shows powdery white scale favoring the palmar creases, and there is moccasin scale of the visible sole. Thus, the next best step in management is to perform a KOH preparation (choice 5) to make the diagnosis of dermatophytosis. Although hand dermatitis is included in the differential, in this scenario it would be inappropriate to start a high-potency topical steroid under occlusion (choice 1) or phototherapy (choice 2) prior to ruling out dermatophytosis. A skin biopsy (choice 3) is not required when KOH, a simple in-office procedure, will suffice to make the correct diagnosis. Patch testing (choice 4) for persistent hand dermatitis helps to rule out allergic contact dermatitis, but in this clinical scenario a KOH preparation should be performed first.

Answer 23

Correct choice: C. 200 Explanation: Eosinophilic folliculitis is characterized by markedly pruritic follicular papules, urticarial and/or pustular, that favor the face, scalp, and upper trunk. It occurs in the setting of immunosuppression, including from HIV infection and following allogeneic hematopoietic stem cell transplantation. In HIV-infected patients, the CD4 count is usually <200 cells/mm3; it may also be a manifestation of IRIS (immune reconstitution inflammatory syndrome). Histologically, lesions are characterized by spongiosis and exocytosis of eosinophils and lymphocytes into the follicular epithelium. In HIV-infected patients, the CD4 count in patients with eosinophilic folliculitis is usually <200 cells/mm3; it may also be a manifestation of IRIS (immune reconstitution inflammatory syndrome).

Answer 24

Correct choice: E. Sodium stibogluconate Explanation: The question stem describes a classic clinio-pathologic presentation of New World mucocutaneous leishmaniasis, which is most often due to L. braziliensis. First line treatment is with a pentavalent antimonial such as sodium stibogluconate or meglumine antimonite. Amphotericin B is the first line treatment for visceral leishmaniasis. The remaining answer choices are not useful in the treatment of New World mucocutaneous leishmaniasis.

Answer 25

Correct choice: C. Valacyclovir 500 mg daily PO Explanation: The dose of valacyclovir for suppressive therapy for herpes simplex virus infections is 500 mg by mouth daily. Patients without significant renal impairment with 4-6 outbreaks of HSV per year (or more) are generally candidates. Valacyclovir 2 g by mouth and repeat dosage in 12 hours is the amount used for intermittent treatment of HSV. Valacyclovir 1 g by mouth TID x 7 days is the dosing schedule for herpes zoster. Abreva and lysine may possibly reduce the duration and severity of HSV outbreaks.

Answer 26

Correct choice: E. Pneumonia due to Streptococcus pneumoniae Explanation: Eczema herpeticum represents rapid dissemination of a herpes simplex viral infection over the eczematous skin of AD patients. It initially develops as an eruption of vesicles, but affected individuals more often present with numerous monomorphic, punched-out erosions with hemorrhagic crusting. Eczema herpeticum is frequently widespread and may occur at any site, with a predilection for the head, neck, and trunk. It is often associated with fever, malaise, and lymphadenopathy, and complications may include superinfection with S. aureus or S. pyogenes as well as herpetic keratoconjunctivitis and meningoencephalitis. Patients with mutations in the filaggrin gene and those who have both severe AD and asthma have an increased risk for eczema herpeticum, and decreased production of antimicrobial peptides may have a pathogenic role. Patients with AD are also predisposed to the development of widespread molluscum contagiosum. Superinfection with Staphylococcus aureus: Eczema herpeticum is often associated with fever, malaise, and lymphadenopathy, and complications may include superinfection with S. aureus or S. pyogenes as well as herpetic keratoconjunctivitis and meningoencephalitis.

Answer 27

Correct choice: B. Sandfly Explanation: This is Leishmaniasis and is transmitted by the sandfly. The sandfly is the vector for Oroya fever/Carrion's disease. Onchocerciasis is transmitted by the blackfly.

Answer 28

Correct choice: A. Fluorescent antibody test for herpes Explanation: This patient has herpes zoster. A direct fluorescent antibody test for the varicella zoster virus can be performed to confirm the diagnosis

Answer 29

Correct choice: A. Syphilis Explanation: This is pemphigus syphiliticus, the only blistering manifestation of syphilis. It occurs in newborns. They have severe bullous lesions.

Answer 30

Correct choice: D. the organism can be cultured from fluid wihtin the blisters Explanation: Most cases of staphylococcal scalded skin syndrome (SSSS) are caused by phage group II strains (e.g. types 55, 71) of S. aureus (which can be methicillin-sensitive or resistant) that produce exfoliative (also know as epidermolytic) toxins. ETA (chromosomally encoded) and ETB (plasmid encoded) are serine proteases that bind and cleave desmoglein 1. This causes splitting of the desmosomes, which leads to disruption of the epidermal granular layer and bulla formation. Desmoglein 1 is targeted by autoantibodies in pemphigus foliaceus, which has identical histological features to SSSS. In contrast to bullous impetigo, where the effects of the ETs are limited to the site(s) of infection, in SSSS the toxin diffuses from a focus of infection and (in the absence of specific antitoxin antibody) spreads hematogenously to produce widespread effects.

Answer 31

correct choice: B. Protozoa Explanation: This is granulomatous leishmania. Leishmania is a protozoa and is located within the macrophages. It is 2-3 microns in size and has a kinetoplast. It rims the macrophages.

Answer 32

Correct choice: B. Rhinoscleroma Explanation: Rhinoscleroma is associated with Klebsiella pneumoniae, ssp. rhinoscleromatis.

Answer 33

Correct choice: A. L donovani, L infantum, L chagasi Explanation: Infections with L. donovani (e.g. India, Bangladesh and the Sudan), L. infantum (e.g. Europe, especially in the setting of HIV infection) and L.chagasi (e.g. Central and South America) are the major causes of visceral leishmaniasis

Answer 34

Correct choice: B. Jarisch-Herxheimer reaction Explanation: The Jarisch-Herxheimer reaction occurs with treatment of syphilis. It is due to TNF- alpha and other cytokines released when the spirochetes are phagocytosed. Tumor lysis syndrome occurs when chemotherapy is started in cancer patients. The isomorphic phenomenon is another name for the Koebner phenomenon. Rumple-Leede sign occurs after release of a tourniquet and there is a shower of petechiae. The Asboe-Hansen sign is when perpendicular pressure is applied to a blister and the blister enlarges. It is seen in pemphigus vulgaris and TEN.

Answer 35

Correct choice: E. Progressive multifocal leukoencephalopathy Explanation: The correct answer is E. The question describes the ampicillin/amoxicillin rash associated with infectious mononucleosis and EBV infection. EBV causes all of the following except for E; JC virus causes PML.

Answer 36

Correct choice: D. Sand fly Explanation: The sand fly causes leishmania which is pictured here. The mango fly causes loa loa. The black fly causes onchocerciasis, the tsetse fly causes African trypanosomiasis.

Answer 37

Correct choice: B. Meningococcus Explanation: Purpura fulminans is an oftentimes dramatic presentation of large ecchymotic areas of the skin, favoring acral sites including the extremities, ears, and nose. The underlying pathophysiology is hemorrhagic infarction of the skin due to disseminated intravascular coagulation. Meningococcal infection is the leading underlying infection associated with sepsis and purpura fulminans. When Kids develop purpura fulminans after an infection the most common cause is group A Strep.

Answer 38

Correct choice: B. Parvovirus B19 Explanation: This is erythema infectiosum, with the slapped cheek appearance. It is due to parvovirus B19. Paramyxovrus causes the measles, molluscum is due to a poxvirus, orf is due to a parapoxvirus. Rubella is due to a togavirus. Coxsackie causes hand-foot-mouth disease and herpangina.

Answer 39

Correct choice: E. The 30-day life cycle is completed within the dermis Explanation: Human scabies is caused by the species-specific, eight-legged mite Sarcoptes scabiei var. hominis shown in the mineral oil prep in the above image. The 30-day life cycle is completed within the epidermis. Acral vesiculopustules can represent a clue to the diagnosis of scabies in infants. Confirmation of diagnosis can be achieved by light microscopic examination of mineral oil preparations of skin scrapings from infested areas for adult mite, eggs or fecal pellets. A scalpel or curette may be used to obtain the skin sample. Microscopic examination of transparent adhesive tape following its application to infested areas of skin represents another diagnostic technique. This image shows an adult female mite and is a light microscopic examination of a mineral oil preparation of a skin scraping in a patient with scabies. 1 – The specific Sarcoptes mite that causes infestation in animals is not a source of human infestation, but can produce bite reactions. 2 – The incubation period before symptoms of scabies develop can range from days to months. In first-time infestations it takes 2-6 weeks before the host’s immune system becomes sensitized to the mite or its by-products, resulting in pruritus and cutaneous lesions. 3 – Each day a female lays 3 eggs which require approximately 10 days to mature. Scabies mites usually live 3 days or fewer off a human host, but may live up to 7 days in patients with crusted scabies. 4 – The scabies mite is 0.35 x 0.3 mm in size and thus is too small to be seen by the naked eye.

Answer 40

Correct choice: B. Desensitization to penicillin Explanation: This is a cutaneous gumma in late syphilis. The treatment for late syphilis is penicillin. If this patient was pregnant and allergic to penicillin the patient would need to undergo desensitization to penicillin and then be treated with penicillin

Answer 41

Correct choice: C. Lesional polymerase chain reaction assay Explanation: Recent recommendations from both the Infectious Diseases Society of America and the American Society for Microbiology characterize lesional nucleic acid amplification testing, such as PCR, as the “most sensitive, specific, and rapid test for diagnosis of HSV-associated skin or mucosal lesions.” Lesional DFA testing or lesional viral cultures may be used to diagnose cutaneous HSV infection, although these tests have lower sensitivity and/or specificity compared to PCR. Blood viral cultures are typically not helpful when trying to diagnose cutaneous HSV infection. Lastly, urine nucleic acid amplification tests can be used to diagnose certain sexually-trasmitted infections (e.g. Chlamydia, Gonorrhea), however they are not helpful for HSV.

Answer 42

Correct choice: B. 10 days to 3 months Explanation: This is a perianal chancre of primary syphilis following anal intercourse. The chancre is non-tender and presents 10 days to 3 months after syphilis exposure.

Answer 43

Correct choice: D. Clarithromycin Explanation: This is a mycobacterial infection after surgery which is usually due to M. Chelonei. It presents with SQ nodules that ulcerate and drain. The treatment is to drain and treat with clarithromycin as first-line antibiotic therapy.

Answer 44

Correct choice: E. HIV infection Explanation: All patients who have syphilis should also be tested for HIV infection

Answer 45

Correct choice: C. Th1 Explanation: This is tuberculoid leprosy which classically has a low concentration of organisms because the body is reacting to the M. leprae. Thus the patients get anesthesia and anhidrosis. There are typically less than three hypopigmented patches. Tuberculoid leprosy is associated with a Th1 cytokine profile including IFN-gamma, IL-2 and IL-12. Lepromatous leprosy is Th2. Tuberculoid leprosy can be either one large red patch with well-defined raised borders or a large hypopigmented asymmetrical spot. Lesions become dry and hairless. Loss of sensation may occur at the site of some lesions. Tender, thickened nerves with subsequent loss of function are common. Spontaneous resolution may occur in a few years or it may progress to borderline or rarely lepromatous types. Leprosy has very characteristic clinical features but the diagnosis must be confirmed because of the need for prolonged treatment with antibiotics. A skin biopsy may show characteristic histopathology with granulomas (mixed inflammatory cell infiltrate in the deeper layers of the skin, the dermis) and involvement of the nerves. Special staining of the tissue may show acid-fast bacilli, the number visible depending on the type of leprosy. Immunohistochemistry stains can be helpful when the bacilli are few in number.The bacteria may also be found in lepromatous leprosy on smears taken from skin slits made in the ear lobes, but the smears will be negative in the tuberculoid or borderline forms of the disease. Lepromatous leprosy. Lepromatous leprosy is a form of leprosy characterized by pale macules in the skin. In lepromatous leprosy, TH2 response is turned on, and because of reciprocal inhibition (IL-4; IL-10), the cell-mediated response (TH1) is depressed.

Answer 46

Correct choice: B. Transmission usually occurs via direct inoculation Explanation: Sporotrichosis is caused by Sporothrix schenckii, a dimorphic fungus found in soil, thorns, moss, and bark. Transmission may occur via direct inoculation or inhalation, though it usually occurs when the fungus enters the skin through a small cut or scrape, usually after someone touches contaminated plant matter. Sporotrichosis has three different forms: lymphocutaneous, fixed cutaneous, and disseminated. The disseminated form is rare. While SSKI may be used to treat lymphocutaneous sporotrichosis, itraconazole is the most common treatment. Cryptococcus neoformans is found in pigeon droppings. Sclerotic bodies (aka Medlar bodies or copper pennies) are seen histologically in chromomycosis (aka chromoblastomycosis), whereas asteroid bodies are typically seen histologically in sporotrichosis.

Answer 47

Correct choice: C. Trichophyton Rubrum Explanation: This is a dermatophyte infection located in the stratum corneum. Trichophyton Rubrum is a common cause of dermatophyte infection. Hortaea werneckii causes tinea nigra, which would show pigmented hyphae on histology. Leishmania presents with amastigotes (tiny dots) within macrophages (Leishman-Donovan bodies); the dermis contains an infiltrate of histiocytes, lymphocytes, and plasma cells. The organisms are best seen with the Giemsa stain.

Answer 48

Correct choice: C. Trichophyton rubrum Explanation: This is tinea corporis, which is most often due to T. rubrum. The remaining answer choices may also produce tinea corporis, but less commonly than T. rubrum.

Answer 49

Correct choice: B. Respiratory Explanation: Varicella is primarily spread via respiratory droplets, and less frequently, direct contact. Varicella is not spread by bloodborne, insect borne, or food borne mechanisms.

Answer 50

Correct choice: D. Warthin-Starry Explanation: Biopsy specimens of bacillary angiomatosis reveal lobular proliferations of capillaries and venules, plump and protuberant endothelial cells, and a marked neutrophilic infiltrate with evidence of leukocytoclasis throughout the interstitium. In H&E-stained sections, interstitial clumps of bacilli appear as purplish granular material. Bacteria can be readily identified with a Warthin– Starry stain. 2- Trichrome stains collagen blue. 3- Verhoeff–Van Gieson stain is used to demonstrate normal or pathologic elastic fibers. 4- Sudan black stains lipids 5- Alzarin redis commonly used in histology to highlight calcium deposits by binding to it by a chelation process. The reaction enable the formation of alizarin red S-calcium, a birefringent compound which deposits appears optically in red.

Answer 51

►A Anogenital and Buschke-Lowentein tumor is caused by HPV 6 and 11. HPV 1 is from palmoplantar warts. HPV 2, 4 causes common warts HPV 7 causes Butcher's warts.

Answer 52

►A Pitted keratolysis is caused by Micrococcus sedentarius. The clinical features are shallow 1 -3mm pits on plantar surface of feet. The treatment is topical erythromycin, clindamycin, or benzoyl peroxide.

Answer 53

►A The picture shown is Impetigo, which is a common, contagious superficial skin infection caused most commonly by staphylococci. Although seen in all age groups, the disease is most common in infants and children. Lesions may involve any body surface but occur most frequently on the 7 exposed parts of the body, especially the face, hands, neck, and extremities. There are two classic forms of impetigo, bullous and nonbullous. Nonbullous impetigo accounts for more than 70% of cases. Historically was caused primarily by group A β-hemolytic streptococci (GABHS), but now appears to be most commonly caused by S. aureus. Anaerobic organisms may also be recovered from lesions of nonbullous impetigo. (Reference: Brook I, Frazier EH, Yeager JK. Microbiology of nonbullous impetigo. Pediatr Dermatol 1997;14(3):192-195.)

Answer 54

►E Staphylococcus Scalded-Skin Syndrome (SSSS) is caused by Staphylococcus exfoliative toxins A and B binding desmoglein 1. This results in the intraepidermal split at the granular layer seen in this illness. Targeting of desmoglein 3 would result in a suprabasilar split. Targeting of plectin, BPAG1, or BPAG2 would result in a subepidermal split. This is not seen in SSSS.

Answer 55

►C Relapsing Fever can be either Louse-borne or Tick-borne. Tick-borne Relapsing Fever is caused by B. duttonii or B. hermsi, while Louse-borne Relapsing Fever is caused by B. recurrentis.

Answer 56

►A Staph scaled skin syndrome is caused by Et-A and ET-B that bind to desmoglein-1. Children under 5 years of age, adults with renal failure or immunodeficiency. Also a Nikolsky's sign is seen in lesional and non-lesional skin with a subgranular blister.

Answer 57

►B Papillomatosis cutis carcinoides di Gottron, also known as Gottron's tumor, is a verrucous carcinoma of the skin. In 1948, Ackerman first described verrucous carcinoma (VC), a low-grade tumor that generally is considered a clinicopathologic variant of squamous cell carcinoma. Verrucous carcinomas are caused by HPV types 6 and 11. When they occur on the feet they are called epithelioma caniculatum. When they occur on the genitals they are refered to as BuschkeLowenstein tumors. When they occur in the mouth they are called Ackerman's tumors or oral florid papillomatosis.

Answer 58

►E Papilloma viruses are non-enveloped,double stranded DNA viruses. Cell mediated responses are primarily responsible for controlling papillomavirus infections. Unlike viruses such as HSV, HPV does not have enzymes required for replication of viral DNA, and is entirely dependent on the host cellular machinery. Recurrent respiratory papillomatosis can be caused by HPV -6 and 11, with verrucous lesions of the airways. It can occur as a juvenile or adult -onset form and present with hoarseness in children. Unlike viruses such as HSV, HPV does not enzymes 9 required for replication of viral DNA, and is entirely dependent on the host cellular machinery for these functions.

Answer 59

►C The most common organism on sebaceous regions of human skin is Propionibacterium acnes. This is an aerotolerant, anaerobic gram positive club-shaped diptheroid that lives in the depths of the sebaceous follicle. It has a potent lipase which cleaves sebaceous triglycerides into glycerol and free fatty acids. The free fatty acids lower the pH and are thought to retard the growth of pathogens such as S. aureus. Other residents of oily regions are: Malassezia furfur, S. epidermidis, Micrococcus luteus and other catalase positive aerobic cocci. S. aureus is a pathogen, and is not considered normal flora of any region of the skin. The other options are found on dry or moist regions of the skin.

Answer 60

►A Measles is caused by an RNA virus known as paramyxovirus. The illness is characterized by high fever, cough, coryza, conjunctivitis, and Koplik's spots. Viral exanthem characterized by erythematous macules and papules beginning on the face and spreading caudally 3-4 days after prodromal symptoms.

Answer 61

►C While warts can be very difficult and frustrating to treat, the spontaneous clearance rate at two years is actually quite high (70-75%).

Answer 62

►A While many subtypes of HPV are associated with genital warts, 6 and 11 are the most common. In general, potentially oncogenic HPV subtypes such as 16 and 18 cause sessile genital warts.

Answer 63

►B The most common subtype of molluscum contagiosum virus is MCV-1. In HIV patients, however, MCV-2 is more common.

Answer 64

►B The recommended treatment for loiasis is Diethylcarbamazine (DEC).

Answer 65

►A Congenital Varicella Syndrome occurs after maternal varicella-zoster virus infection early in pregnancy (up to 20 weeks gestation).

Answer 66

►A Dermatobia hominis is most common agent of cutaneous and furuncular myiasis in North America, but Cuterebra spp. are also a frequent cause of furuncular myiasis in the US. Complications of myiasis are tetanus and secondary bacterial infection.

Answer 67

►D The image shows sparsely distributed hemorrhagic vesiculopustules with erythematous bases on an acral surface. These features are characteristic of gonococcemia.

Answer 68

►B The most likely diagnosis is Erysipelas which is caused by beta -hemolytic group A streptococcus. The treatment of choice is intravenous penicillin.

Answer 69

►B Orf virus infection is also known as Ecthyma contagiosum. Ecthyma Gangrenosum is caused by Pseudomonas aeruginosa. Ecthyma is caused by Staphylococcal or streptococcal pyoderma. Pseudocowpox and Milker's nodule are also known as paravaccinia and caused by udders of infected cows.

Answer 70

►A The question stem describes signs and symptoms of hyponatremia. The syndrome of inappropriate antidiuretic hormone secretion is a known, albeit rare, complication of varicella zoster virus infection. The other four answer choices are also known complications of varicellazoster virus infection, but do not cause the disease presentation as described.

Answer 71

►A Children who are actively infected with the measles virus are commonly found to have lymphopenia. While an abnormality of any of the blood cell lines is possible during viral infections, in the case of measles infections, lymphopenia is most common. However, cbc may reveal a relative lymphocytosis and thrombocytopenia.

Answer 72

►A Relapsing fever is caused by the human body louse Pediculus humanus and the borrelia species is B. recurrentis. The clinical features are paroxysmal fevers, headache, lymphocytoma, mylagias, erythematous or petechial macules on trunk and extremities.Louse-borne relapsing fever is transmitted by the human body louse and is generally restricted to refugee settings in developing regions of the world.Tick-borne relapsing fever has the same symptoms occurs in the western United States and is usually linked to sleeping in rustic, rodent-infested cabins in mountainous areas. The vector for tick borne is ornithodoros and it is due to Borrellia duttonii.

Answer 73

►A Chancroid is a sexually transmitted disease caused by the bacteria Hemophilus ducreyi. It is one of many organisms that can cause a genital ulcer. Chancroid is characterized by a soft, painful chancre with ragged edges. Giemsa stained sections reveal a "school of fish" configuration which is typical. Treatment is with azithromycin, ceftriaxone, ciprofloxacin, or erythromycin.

Answer 74

►C Epithelioma cuniculatum is a form of verrucous carcinoma involving the sole.

Answer 75

►C The first stage of this condition is known as Carrion‟s disease, which can be fatal. It was in Dr. Carrion (as a medical student), who self inoculated himself to prove that the cause of verruga peruana (the second stage described above) was the same as that of the first stage. The cause of both Carrion‟s disease and verruga peruana is Bartonella bacilliformis. B. henselae is the cause of Cat Scratch disease while B. quintana causes Trench Fever. Rickettsia rickettsii is the cause of Rocky Mountain Spotted Fever and Rickettsia akari causes Rickettsial pox.

Answer 76

►D Confirmation of infection with Leishmaniasis is performed by culture in Novy-MacNeal-Nicolle (NNN) medium.

Answer 77

►D The most common presentation of intra-oral involvement of EBV infection is pinpoint petechiae of the junction of the hard and soft palate. The associated eponym is Forchheimer spots. Forchheimer spots are not pathognomonic for EBV infection, as they can be seen in measles, rubella, and scarlet fever. While oral hairy leukoplakia is associated with EBV infection, it is not the most common mucous membrane sign.

Answer 78

►A Although rare, onychomadesis has been associated with enteroviral infections, including handfoot- mouth syndrome due to Coxsackie virus. Onychomadesis is an idiopathic shedding of the nails beginning at the proximal end. It may be due to temporary arrest of the matrix during the infection. In most cases, the nails return normally.

Answer 79

►A In any child with peri-anal warts, the possibility of sexual contact must be excluded. Fortunately, in infants up to 12 months of age, the most common route of acquisition of the human papilloma virus is vertical transmission at the time of delivery.

Answer 80

►C Epidermodysplasia verruciformis is caused by HPV types 5, 8, 9, 12, 14, 15, 17, 19-26.

Answer 81

►A First line therapy for SSSS includes IV penicillinase resistant penicillin. Second line therapy is IV macrolide treatment. Third line therapies are cephalosporin and vancomycin. Clindamycin is added to curtail toxin production.

Answer 82

►C Gonorrhea, caused by a gram negative intracellular diplococcus, often presents cu taneously with hemorrhagic vesiculopustules of the distal extremities. Septic arthritis is also an important presentation of gonococcemia, most commonly involving the knee.

Answer 83

►D This patient has a type III reactional state to leprosy called Lucio's phenomenon. It mostly occurs in people of Latin American descent and is characterized by rapidly ulcerating and bullous lesions usually on the legs. It has a high mortality rate. A type I reaction, or a reversal/upgrading reaction, can occur after treatment and are associated with a change in cell-mediated immunity and result in accelerated destruction of bacilli. This is manifested as inflammation of existing lesions with no systemic symptoms. A type II reaction, or erythema nodosum leprosum, represents an immune complex deposition and features widespread erythematous nodules with systemic features. Lofgren's is associated with sarcoidosis.

Answer 84

►A This is bacillary angiomatosis and is caused by Bartonella hensalae and can be associated with contact with cats in 20% of cases and occurs in patients with AIDS. The disease is treated with a macrolide antibiotic or doxycycline.

Answer 85

►D Eosinophilic pustular folliculitis is a pruritic disorder that may be seen in HIV positive patients. Typically, the CD4 count is < 300. In patients with HIV, pruritus tends to improve after institution of anti-retroviral therapy.

Answer 86

►D The most likely diagnosis is malacoplakia. Malacoplakia, an infection usually attributed to S. aureus, P. aeruginosa, or E. coli is characterized histopathologically by Michelis -Gutmann bodies. These are foamy eosinophilic macrophages containing calcified, laminated, intracytoplasmic bodies. They can be highlighted by a calcium stain such as von Kossa. CD3 and CD20 are lymphocyte markers, von Gieson is an elastic tissue stain, and Steiner stain is used to highlight spirochetes. These would not aid in the diagnosis of malacoplakia.

Answer 87

►B The main deterrent to staphylococcal infection is the neutrophils. These contain bactericidal chemicals and proteins such as myeloperoxidase-H202-halide, lysozyem, serine proteases, defensins and bacterial permeability increasing peptide. Complement serves as an effective opsonin for phagocytosis by circulating neutrophils and macrophages. Immunoglobulin response hastens phagocytosis but is not absolutely required. Cytotoxic T-cells do not play a major role in controlling S. aureus infections.

Answer 88

►C Hutchinson's sign is defined by vesicles at the nasal tip in a patient with facial herpes zoster. It is caused by VZV invovlement of the nasociliary nerve. Patients suffering with this sign should be screened for ophthalmologic herpes zoster invovlement.

Answer 89

►A Cat scratch disease is caused by B. henselae. It is from the flea-Ctenocephalides felis. It spontaneous resolution in most of cases.

Answer 90

►A Anthrax is caused by Bacillus anthracis, a gram positive spore-forming rod. Anthrax is primarily seen in individuals who are in contact with wild or domestic animals. Recent cases have been linked with bioterrorism. B. anthracis produces edema toxin and lethal toxin. Edema toxin is comprised of edema factor and protective antigen. Edema factor is a calmodulin dependent adenyl cyclase. The increased cAMP induces the gelatinous edema of anthrax skin lesions.

Answer 91

►B The reduviid big is the vector of American trypanosomiasis (Chagas disease). The vector of African trypanosomiasis is the tstse fly.

Answer 92

►C Larva migrans is caused by Ancylostoma braziliense, a hookworm of cats and dogs. It does not leave the epidermis because it lacks collagenase. Larva currens is due to strongyloides and presents with serpiginous lesions on the buttock, thighs or perianally. Ground itch is due to ancylostoma duodenale and necator americanus which clinically present like cutaneous larva migrans but are able to leave the epidermis, therefore causing fuplomany infiltrates and eosiniophilia. Loeffler's syndrome, is the name for the patchy infiltrate of the lungs with eosinophilia. Treatment for this parasitic infection is ivermectin or albendazole or thiabendazole.

Answer 93

►B 13-cis-retinoic acid (isotretinoin/Accutane) is a derivative of vitamin A. It has several mechanisms of action in acne. It rapidly suppresses sebum production, causing a decrease in P. acnes populations. It also decreases follicular plugging by an uncertain mechanism. Vitamins D, K and E are fat soluble vitamins, but are not able to completely arrest the disease process in acne. Vitamin B3 is niacin and is associated with a diet of exclusively of corn, millet or sorghum. Other sources: carcinoid, Hartnup disease, parasites, GI disorders, IV nutrition, and psychiatric disease. Findings include the 3 D‟s: Diarrhea, Dementia, Dermatitis.

Answer 94

►C TNF-alpha. The Jarisch-Herxheimer reaction is associated with increased plasma concentrations of TNF-alpha after antibiotic treatment of syphilis. The Jarisch-Herxheimer reaction has also been described following treatment of louse-borne relapsing fever, lyme disease and leptospirosis.

Answer 95

►D Herpes simplex virus and disseminated varicella-zoster virus infection can be difficult to distinguish clinically and histologically. These viruses share the histologic findings of margination of nuclei, multinucleated cells, and nuclear molding. The presence of leukocytoclastic vasculitis favors a diagnosis of disseminated varicella-zoster virus.

Answer 96

►E Anthrax, also known as woolsorter‟s disease or malignant pustule is caused by Bacillus anthracis, a gram positive rod. It is primarily caused by contact with infected wild or domestic animals or their products (such as wool). This organism has 3 clinical forms: inhalation, gastrointestinal and cutaneous. The primary lesion is a “malignant pustule” which begins as a painless papule that evolves into a hemorrhagic bulla. Ultimately, a black eschar forms. The lack of pain is helpful in distinguishing between anthrax and other infections of the skin which are painful, such as ecthyma. The other listed organisms are not causes of this disease.

Answer 97

►A Necrolytic acral erythema is characterized by hyperkeratotic well-defined plaques on the lower extremities, seen occasionally in patients with hepatitis C virus infection. Treatment consists primarily of treating the underlying infection. Diet supplementation with zinc has been shown to improve necrolytic acral erythema, even in the presence of normal serum zinc levels.

Answer 98

►A This patient has African trypanosomiasis. It is caused by T. brucei gambiense and T. brucei rhodesiense and the vector is the Tsetse fly. Posterior cervical lymphadenopathy is known as winterbottom's sign. Romana's sign is eyelid edema and conjunctivitis at the site of inoculation for American trypanosomiasis.

Answer 99

►B Lymphogranuloma venereum presents as a painless ulcer and is caused by Chlamydia trachomatis serotypes L1, L2, L3. While buboes can be aspirated, they should not be incised and drained. Transmission occurs through sexual contact, but can occur via skin-to-skin contact. Complications of late stage disease include proctocolitis, perirectal abscesses, rectovaginal fistulas, and anal fistulas.

Answer 100

►A The fluorescent treponemal antibody absorption test is the most sensitive serologic test in primary syphilis. The ELISA is the test of choice in early primary and congenital syphilis because it is the first to become reactive. However, it is less sensitive in late primary syphilis because of reduction of IgM production. The ELISA is 100% specific. MHA-TP is less sensitive than FTA-ABS during primary syphilis. Syphilis can be detected during the early infectious stages by taking swabs of the chancre for polymerase chain reaction (PCR). Dark-field microscopy examination of tissue or tissue fluid from a primary ulcer (chancre) or condylomata lata is now less commonly undertaken than in the past. Blood for serological tests is necessary for diagnosis. Serological tests turn positive about 5 to 6 weeks after acquiring the infection. In some cases, cerebrospinal fluid can be tested to confirm neurosyphilis. Non-specific non-Treponemal tests eg Rapid plasma reagin (RPR), Venereal disease research laboratory (VDRL) May cross-react resulting in low-level false-positive tests during pregnancy, other infections, drug abuse, connective tissue disease and aging. Levels usually relate to disease activity and are used for monitoring treatment. After effective treatment of syphilis, these tests usually become negative but in some people, may remain positive at low levels Specific anti-treponemal antibody tests eg Treponenam pallidum particle agglutination assay (TPPA), enzyme immunoassays (EIA or AIA), fluorescent treponemal antibody absorption (FTA- ABS), microhaemagglutination assay (MHA-TP) and Western Blot (WB). These detect antibody due to past or present infection with T. pallidum or another Treponema species (eg yaws or pinta) They cannot distinguish between different types of Treponemal infection eg yaws or syphilis or the duration of infection. Most people with reactive treponemal tests will continue to have reactive tests for the remainder of their lives, regardless of treatment or disease activity. An EIA test is sometimes used as a screening test, as it avoids the false positives found when RPR or VDRL are used.Skin biopsy may or may not show characteristic histopathological features. Molecular testing using polymerase chain reaction (PCR) can confirm the presence of genetic material from the bacteria in ulcers, on the skin surface, in blood, lymph nodes and other tissue. Reference: Forrestel AK, Kovarik CL, Katz KA. Sexually acquired syphilis: Laboratory diagnosis, management, and prevention. J Am Acad Dermatol. 2020 Jan;82(1):17-28. doi: 10.1016/ j.jaad.2019.02.074. Epub 2019 Apr 12. Review. PMID: 30986474

Answer 101

►D Infectious mononucleosis is characterized by a sore throat, painful lymphadenopathy, fatigue, and splenomegaly. The formation of a morbilliform rash upon challenge with ampicillin or related antibiotics is a classic finding. The most common virus associated with infectious mononucleosis is Epstein-Barr virus. The incubation period is relatively long, 3-7 weeks.

Answer 102

►A Edema factor is a portion of the edema toxin, one of two exotoxins secreted by Bacillus anthracis. Edema factor causes gelatinous edema of anthrax skin lesions by inducing an increase in cyclic adenosine monophophate levels. Lethal toxin, the other exotoxin, works by releasing tumor necrosis factor-alpha and interleukin-1 beta.

Answer 103

►D The cutaneous features of Exanthem Subitum (Roseola infantum, Sixth Disease)as described in the question develop as the fever subsides. While the other diagnoses are part of the differential diagnosis of "fever and rash" in children, only roseola infantum has this characteristic clinical course.

Answer 104

►A The case presentation describes an infection with Vibrio vulnificus, a Gram-negative rod, which may lead to a rapidly expanding cellulitis, with hemorrhagic bullae and necrosis, and lifethreatening septicemia. This infection mainly occurs along the Atlantic seacoast. It may be acquired after ingesting raw oysters or other seafood. Alternatively, localized skin infection may result after exposure of an open wound to seawater. Doxycycline together with ceftazidime is the treatment of choice. In patients with preexisting hepatic dysfunction or immunocompromise and whose wounds are exposed to or acquired in saltwater, prophylactic antibiotic coverage with doxycycline, 100 mg every 12 h, and cleansing with 0.025% sodium hypochlorite solution may prevent progressive infection.

Answer 105

►D Ticks are capable of transmitting:Lyme disease-Borrelia burgdorferi, a tickborne spirochete. Tularmia-Francisella tularensis, bite of a tick. Rocky Mountain spotted fever-Rickettsia rickettsii, tick typhus. Yaws-Treponema Palladium, subspecies pertunue-transmitted nonsexually, by contact with infectious lesions. Ehrlichiosis-Ehrlichia chaffeensis, tickborne

Answer 106

►A Herpetic whitlow is more commonly caused by HSV2 from digital/genital contact. It can also occur in dentist.

Answer 107

►D S. aureus rapidly becomes a member of the cutaneous flora in locations where there is serum or plasma on the skin. Often patients with atopic dermatitis will have colonization of this organism in lesions and may benefit from topical or oral antibiotics. P. avidum and aerobic diphtheroids are present in moist regions of the skin. Gram positive coagulase negative cocci are the dominant organism in the dry regions of the body. S. epidermidis is most commonly found in oily body regions.

Answer 108

►E Focal epithelial hyperplasia is caused by HPV-13 and 32.

Answer 109

►A Mixed cryoglobulinemia is characterized by LCV and the finding of monoclonal or polyclonal IgG and IgM cryoglobulins in the blood. Mixed cryoglobulinemia is commonly associated with HCV infection. Patients with HCV-associated mixed cryoglobulinemia are at an increased risk of developing non-Hodgkins lymphoma, approximately 35 times the general population.

Answer 110

►A Cat scratch disease is caused by infection with B. henselae - a gram-negative bacillus of the genus Bartonella.

Answer 111

►D Guarnieri bodies are cytoplasmic eosinophillic inclusions found on light microscopy.

Answer 112

►A Visceral leishmaniasis is the most severe form of leishmaniasis. Complications can be fatal, and include pneumonia, tuberculosis, and dysentery, which are potential opportunistic infections. Visceral leishmaniasis is most commonly caused by L. donovani and L. infantum.

Answer 113

►A The most important determinant of the skin‟s protection against infectious agents is the mechanical barrier of intact skin. The dryness of the skin is also important in retarding infection. The resident flora may help prevent colonization by pathogenic organisms, but is not the most important factor. Immunoglobulins are present on intact skin in miniscule amounts. The cornified cell envelope is not a major determinant of infection prevention.

Answer 114

►E B. anthracis has 2 exotoxins: edema toxin and lethal toxin, each comprised of a pair of noncovalently linked proteins: “ Edema toxin = Edema Factor (EF) + Protective Antigen (PA) “ Lethal toxin = Lethal Factor (LF) + PA “ EF causes gelatinous edema of anthrax skin lesions by inducing an increase in cyclic adenosine monophosphate (cAMP) levels “ LF causes shock and death in disseminated anthrax via the release of tumor necrosis factor-alpha (TNF-a)and interleukin-1b (IL-1b) “ PA is responsible for entry of exotoxins into the cell by receptormediated endocytosis.

Answer 115

►A Tularemia represents a wide range of clinical syndromes caused by Francisella tularensis. The bacterium is most commonly acquired through contact with infected animals, including rabbits. There are a wide variety of variants, with the ulceroglandular form being most common. Ulceroglandular tularemia is characterized by a chancre-like ulcer with raised borders and regional lymphadenopathy, most commonly on the finger or hand. Treatment is with streptomycin.

Answer 116

►C The Bushke-Lowenstein tumor is caused by HPV-6 and 11.

Answer 117

►D Tularemia, which is caused by Francisella tularensis, occurs after exposure to infected animals, including, rabbits, foxes, and squirrels. The clinical description is that of the ulceroglandular form, which is the most common presentation.

Answer 118

►D The ulcerated nodule shown here is characteristic Leishmaniasis is treated with pentavalent antimony. of cutaneous leishmaniasis (CL).

Answer 119

►A Chronic purulent nodules with granular bodies seen in patients with immunosuppresion, diabetes, and alcoholism is called botryomycosis. Causative organisms include S. aureus, P. aeruginosa, E. coli, and Proteus species. Scrofuloderma is cutaneous extension of underlying Mycobacteria tuberculosis infection. Rhinoscleroma is caused by Klebsiella pneumoniae rhinoscleromatis. Ecthyma gangrenosum is typically seen following Pseudomonas septicemia. Erysipeloid is caused by Erysipelothrix rhusiopathiae.

Answer 120

►B Corynebacterium tenuis is responsible for causing trichomycosis axillaris, a superficial bacterial overgrowth of axillary hairs characterized by circumferential yellow (most common), red, or black granular concretions. Majocchi's granuloma is a dermatophyte infection. Erysipelas is caused by beta-hemolytic group A streptococcus. Malakoplakia is usually caused by S. aureus, P. aeruginosa, or E. coli. Erysipeloid is caused by Erysipelothrix rhusiopathiae. Corynebacterium minutussimum is the causative organism in erythrasma and pitted keratolysis.

Answer 121

►E Patients with meningococcemia often demonstrate deficiencies of late complement components C5-9.

Answer 122

►A Trichomycosis axillaris is caused by Corynebacterium tenius. It is a yellowish brown concretions on axillary hair shafts. Treatment is shaving, benzoyl peroxide gel, and topical erythromycin.

Answer 123

►D Loiasis is caused by the nematode loa loa. It is transmitted by the mango fly (Chrysops dimidia or CHrysops silacea). It may manifest with painful, localized subcutaneous nonpitting edema called calabar swellings. Conjunctival migrations are also common.

Answer 124

►A Eikenella corrodens is common in human bite infections. Pasteurella multocida is usually from cat bites and Pasteurella canis is from dog bites.

Answer 125

►A The best site for diagnosis of rabies is a biopsy from the neck. This virus has an incubation period of 5 days to 1 year and demonstrates retrograde axoplasmic flow until it reaches the spinal cord. It subsequently undergoes centrifugal spread along the peripheral nerves to the skin, intestine, and into the salivary glands where it is shed.

Answer 126

►C The annual risk of developing herpes zoster in an HIV infected individual, regardless of the CD4 count, is approximately 3%.

Answer 127

►B This patient has gnathostomiasis caused by Gnathostoma dolorosi or spinigerum. It is commonly acquired from freshwater fish. It manifests with migratory intermittent erythematous urticarial plaques that recur every 2-6 weeks. The plaques move about 1 cm/day. Histology shows eosinophilic panniculitis. Treatment is surgical removal or albendazole.

Answer 128

►C Mikulicz”s cells are foamy macrophages found in Rhinoscleroma “ a chronic, inflammatory, granulomatous disease of the upper respiratory tract. Virchow cells are found in Hansen”s disease. Hansemann cells and Michaelis-Gutman bodies are found in Malakoplakia.

Answer 129

►B Kaposi's sarcoma is a vascular neoplasm seen most commonly on the lower extremities, back, and genitaliae. In the United States, this disease is most commonly seen in patients with AIDS. Kaposi's sarcoma has been linked to infection with HHV-8. 20% of men with Kaposi's sarcoma will have detectable HHV-8 in their semen.

Answer 130

►A Carrion's disease, or Oroyo fever, is caused by Bartonella bacilliformis and is transmitted via the Lutzomyia sandfly. It is characterized by fevers, headache, arthralgias, and an acute eruptive stage that resembles bacillary angiomatosis. It has an untreated fatality rate of 40% secondary to salmonella infection; chloramphenicol is given with tetracycline for treatment. Epidemic typhus may also coexist with salmonella.

Answer 131

►E Xenopsylla cheopis (rat flea) is the vector of endemic typhus, which is caused by R. typhi.

Answer 132

►E Symptoms of congenital CMV infection include low birth weight, microcephaly, seizures, petechial rash, and hepatosplenomegaly. Fortunately, the vast majority (90%) of congenital CMV infections are asymptomatic.

Answer 133

►C In addition to TSST-1 which is present in 50% of non-menstrual cases of TSS, enterotoxins, especially B & C, cause TSS. These enterotoxins are also superantigens, which recognize the V -beta region of the T-cell receptor. Coagulase clots plasma, Penicillinase degrades penicillin, Hemolysin lyses red blood cells and exfoliatin splits the epidermis (antigen is desmoglein 1).

Answer 134

►A The Jarisch-Herxheimer Reaction is characterized by fever, headache, lymphadenopathy, myalgias, and elevated white blood cell count. It is caused by the release of inflammatory cytokines, particularly TNF-alpha, due to phagocytosis of spirochetes following antibiotic administration.

Answer 135

►D The most likely cause of a non-healing ulceration in someone who has been in a tropical location is M. ulcerans. M. marinum causes inflammatory nodules following injury in an aquatic environment. M. chelonei is a rapidly growing organism most commonly found in soil, water, dust and animals which presents as single/multiple erythematous SC nodules on an extremity or following a surgical procedure. M. kansasii rarely causes skin lesions. L. donovani is a causse of visceral leishmaniasis in India and Kenya (kala-azar).

Answer 136

►E Calabar swellings are characteristic of Loiasis. They are transient, non-tender soft tissue swellings found most commonly around joints.

Answer 137

►D The most likely diagnosis is H. flu cellulitis. This infection usually occurs in children and is characterized by a single indurated plaque with poorly delineated margins. Erysipelas, an infection caused by beta-hemolytic streptococcus group A, usually presents with well delineated margins in adult patients.

Answer 138

►C Oral hairy leukoplakia is an oral mucosal infection most often caused by the Epstein-Barr virus, which occurs in immunocompromised patients. Clinically, thick, white plaques are noted on the lateral sides of the tongue, often fissured.

Answer 139

►C Multiple crateriform pits on the feet following suboptimal hygiene most likely is pitted keratolysis caused by Micrococcus sedentarius. Treatment is topical erythromycin, clindamycin or benzoyl peroxide. This is not Gorlin‟s syndrome (Basal Cell Nevus syndrome). While these pits are common, it is not a variant of normal. A skin biopsy could confirm the diagnosis, but is not necessary. A Wood‟s lamp would not be particularly helpful. Some believe that Corynebacterium spp. also cause this condition, but that is still theory and not proven.

Answer 140

►B Roseola infantum may be cause be either human herpes virus types 6 or 7. It is the sixth of the traditional exanthems of childhood. A diffuse, maculopapular eruption is typically preceded by a prodrome of fever and either respiratory or gastrointestinal symptoms. The infection usually occurs in the spring and the fall and nearly all children are seropositive for the virus by the age of 4.

Answer 141

►A Butcher's warts are caused by HPV type 7.

Answer 142

►C Vaccinia immune globulin can be administered to treat some of the complications associated with vaccinia vaccination. Vaccinia immune globulin is indicated for inadvertent inoculation with extensive involvement or ocular implantations, eczema vaccinatum, generalized vaccinia (severe or recurrent), and progressive vaccinia. It is not recommended for inadvertent inoculation with mild reaction, generalized vaccinia (mild or limited), post-vaccination encephalitis, and isolated vaccinia keratitis.

Answer 143

►A Toxic shock syndrome (TSS) is mediated by Enterotoxins B and C (50% of nonmenstrual cases) and TSS toxin 1 (TSST-1), which is the leading cause of menstrual cases.

Answer 144

►A A tuberculid is a cutaneous immunologic reaction to tuberculosis elsewhere in the body. By definition, cultures and stains for M. tuberculosis are negative. Erythema induratum of Bazin/Nodular vasculitis present as erythematous or cyanotic nodules on the posterior calves. 85% of cases occur in women. The other listed presentations of TB are all due to secondary spread from an established TB infection at another location. In some cases, organisms can be recovered and cultures may be positive.

Answer 145

►C Patients that are pregnant or for children <9 years old, the treatment for lyme disease is amoxicillin. Lyme disease is caused by B. burgdorferi. Clinical signs are erythema migrans and acrodermatitis chronica atrophicans.

Answer 146

►A Polyarteritis nodosa is characterized by the onset of painful nodules on the lower extremities. It can be limited to the skin (cutaneous PAN), or can involve a wide variety of organ systems (systemic PAN). Approximately 7-8% of cases of polyarteritis nodosa cases are associated with Hepatitis B virus infection.

Answer 147

►D Actinomyces israelii is an anaerobic gram-positive rod which causes chronic suppurative nodules and sinus tracts with an exudate containing sulfur granules. It most commonly effects the cervicofacial area, especially near the mandible. The abdomen and thoracic areas can also be affected. The source of infection is endogenous and patients with poor oral hygiene, penetrating foreign bodies, and recent dental procedures are at increased risk. Treatment of choice is penicillin.

Answer 148

►C Ulcers in the genital area in sexually active patient generally fall into two groups: painful and painless. Painless ulcers include syphilllis, lymphogranuloma venereum, and granuloma inguinale. The primary cause of painful erosion or ulcer is H. ducreyi or herpes simplex. An ulcer with a ragged edge that is painful is characteristic of H. ducreyi. The treatment of choice is azithromycin.

Answer 149

►D Chancroid classically presents with a soft, tender chancre with ragged edges and unilateral, tender inguinal adenopathy (bubo). A “school of fish” pattern on Gram or Giemsa stain is diagnostic.

Answer 150

►C Botryomycosis is an uncommon, chronic, idonlent disorder characterized by nodular, crusted, purulent lesions. Sinuses that discharge sulfur granules are present. These heal with atrophic scars. The granules yield most commonly Staphylococcus aureus on culture, although cases caused by Pseudomonas aeruginosa, E. coli, Proteus, Bacteroides, and Streptococcus have been reported

Answer 151

►D Paramyxovirus is a single-stranded RNA virus. All other listed choices are DNA-based viruses.

Answer 152

►A This patient has congenital late syphilis, seen in children over two years of age. The unilateral enlargement of the medial clavicle is called the Higoumenaki's sign. These patients also can have Hutchinson's teeth or widely-spaced, peg-shaped teeth in the upper incisors. They can also have a saddle nose and saber shins.

Answer 153

►A Histoplasmosis is associated with bird and bat droppings and is seen in the mississippi and ohio river valleys in conjunction with inhalation of microconidia.

Answer 154

►C Oral hairy leukoplakia is characterized by a white patch with a corrugated surface on the side of the tongue. It is generally asymptomatic. Oral hairy leukoplakia is seen most commonly in patients with defective cell-mediated immunity, in particular HIV infection. Oral hairy leukoplakia is associated with EBV opportunisitc infection, among other viruses. 33% of patients with HIV will have oral hairy leukoplakia.

Answer 155

►B The sandfly belonging to the genus Lutzomyia is the vector of New World Leishmaniasis. Sandflies of the genus Phlebotomus are the vectors of Old World Leishmaniasis.

Answer 156

►A Recurrent orolabial herpes simplex virus infection is a very common problem. In many cases, the cause of the recurrences is idiopathic. Identifiable triggers include light exposure and emotional stress, among others. UVB is the most commonly implicated factor.

Answer 157

►C Verruga peruana, a disease endemic to Peru and a few neighboring countries, is caused by Bartonella bacilliformis. It is transmitted by the sandfly, Lutzomyia verrucarum. It is preceded by an acute febrile stage called Oroyo fever or Carrion”s disease. The treatment of choice is chloramphenicol.

Answer 158

►C Lymphatic filariasis is spread by mosquitoes belonging to genera Aedes, Anopheles, Culex, or Mansonia.

Answer 159

►A Loiasis is caused by the organism Loa Loa. The vector is mango flies. The clinical characteristic is calabar swelling and adult worm migrating across conjunctivae or "eye worm". The treatment is DEC or diethylcarbamazine.

Answer 160

►D Ecthyma gangrenosum is an infection of critically ill or immunocompromised individuals by Pseudomonas aeruginosa. Clinically, patients develop opalescent, tense vesicles or pustules surrounded by a narrow pink to violaceous halo. The lesions rapidly become hemorrhagic, then violaceous and necrotic leaving ulcers. The most common location is on the buttocks and lower extremities. Treatment is with aminoglycosides.

Answer 161

►C The proncipal vector of Lyme Disease in the Northeastern U.S. is Ixodes dammini (Ixodes scapularis).

Answer 162

►A Congential sphyilis can be passed from the mother to the child. Dental findings are called hutchinson teeth and mulberry molars.

Answer 163

►B Leishmaniasis is a parasitic infection born by a sandfly vector. No treatment is necessary for cutaneous leishmaniasis, pentavalent antimony for visceral leishmaniasis and mucocutaneous. Mazzotti reaction is used to test for onchocerciasis in which a single dose of dimethycarbamazine is given for reaction. Amphotericin B is only used in pentavalent antimo ny resistant cases.

Answer 164

►D Smallpox is an acute exanthematous infection caused by the variolae poxvirus. It is transmitted primarily by respiratory secretions as well as more infrequently skin inoculation and fomite spread. Following contact, there is an asymptomatic period of 12-13 days. Following the asymptomatic period, patients develop a prodrome of fever, headache, back pain and vomiting for 3 days. Then, the characteristic deep seated papules that vesicles appear. These lesions mature into a pustule with a central umbilication. Occasionally, patients may develop a hemorrhagic form of the disease which is associated with thrombocytopenia and poor prognosis. Vaccination is not contraindicated in children under 5.

Answer 165

►B This is an example of secondary syphilis. It involves the skin and mucous membranes. It also lasts for 4 to 12 weeks. It involved widespread cutaneous eruptions, ham-colored macules on the palms and soles, mucous patches, condyloma lata, split papules and moth eaten alopecia.

Answer 166

►A Actinomycosis is a chronic suppurative infection forming nodules and sinus tracts with an exudate containing sulfur granules. Risk factors include poor oral hygiene, penetrating foreign bodies, and dental procedures. The causative organism is Actinomyces israelii, an anaerobic gram-positive rod.

Answer 167

►C These three are rapid grower mycobacteria and the treatment of choice is clarithryomycin. Minocycline can also be used, but it considered second line in WHO treatment.

Answer 168

►C Non-treponemal tests for syphilis measure antibodies against phospholipids released from treponemes and damaged host cells. False positive non-treponemal tests can occur in the setting of pregnancy, autoimmune diseases, other spirochete infections, and infectious diseases such as leprosy and malaria. It does not occur in cases of melanoma.

Answer 169

►A Certain HPV subtypes have been shown to induce neoplasia, including cervical cancer. There are many high-risk subtypes, including 16, 18, 31, and 33. The HPV early genes E6 and E7 bind the tumor suppressors p53 and retinoblastoma protein, respectively, inactivating them and initiating oncogenesis.

Answer 170

►A This patient developed an acute reaction to dimethylcarbamazine indicating a Mazzotti reaction. This reaction is seen with onchocerciasis. Appropriate treatment for onchocerciasis, caused by Onchocerca volvulus, is ivermectin. These patients may demonstrate pruritus, dermatitis, leopard skin, onchocercomas (nodules with microfilariae) and blindness.

Answer 171

►C Scabies is caused by the mite Sarcoptes scabiei var. hominis. The life cycle of the mite is 30 days. A female mite will lay 60-90 eggs during her life.

Answer 172

►D Winterbottom‟s sign (posterior cervical lymphadenopathy) is a clinical feature of African trypanosomiasis. Romaña‟s sign (eyelid edema and conjunctivitis at site of incoculation) is a diagnostic finding in American trypanosomiasis (Chagas‟ disease).

Answer 173

►B Malakoplakia is a multi-organ inflammatory granulomatous disease that most frequently arises in the setting of immunosuppression. Common sites of involvement include the genitourinary, lung, lymph nodes and bone. Cutaneous involvement is rare, and typically presents as asymptomatic papules, nodules, or plaques. Lesions may have associated erosions or ulcerations, and sinus tracts may be seen. While skin lesions are non-specific, histopathology reveals foamy dermal histiocytes known as von Hansemann cells which contain basophilic granular inclusions. The latter are known as Michaelis-Gutmann bodies and are considered pathognomonic for malakoplakia. Michaelis- Gutmann bodies are comprised of calcium, iron, and phosphate salts, and hence stain positively with von Kossa, Perls, and PAS, respectively. The pathophysiology of malakoplakia is thought to arise from an acquired defect in macrophage activation in response to bacterial infection, most commonly. E. coli. Treatment for cutaneous lesions is surgical excision, although recurrence is not uncommon.

Answer 174

►D Carrion's disease (Oroya fever) is characterized by fevers, headaches and arthralgias and is accompanied by severe hemolytic anemia. Superinfection with Salmonella is the most frequent cause of death. Protection from sandfly bites is all-important.

Answer 175

►C Tularemia is a zoonotic disease caused by the gram-negative coccobacillus Francisella tularensis. It is transmitted by ticks: dog tick, wood tick, lone star tick, or from deer flies (Chrysops) or from contact with infected mammals (usually rabbits) or from infected water. It characteristically presents as an acute febrile illness with other variable clinical manifestations depending on the route of inoculation. Possible symptoms could include an ulcer at the site of inoculation, pharyngitis, ocular lesions, lymphadenopathy, and pneumonia. Diagnosis can be made by culture or a fourfold titer change. Because of its potential use as a biologic agent, tularemia is once again a reportable disease.

Answer 176

►A Tuberculoid leprosy has a TH1 cytokine profile of IFN gamma, IL-2, IL-12. It is paucibacillary, Lepromin test +. There is less than 3 lesions and anesthetic and anhidrotic lesions.

Answer 177

►C Exanthem Subitum (Roseola Infantum, Sixth Disease) is caused by human herpesvirus 6, and 7 (HHV-6, HHV-7).

Answer 178

►A The butcher warts are associated with HPV-7. Laryngeal carcinoma is associated with HPV-30. Common warts are HPV 2, 4.

Answer 179

►C Erythrasma is caused by corynebacterium minutissimum. The presence of coprophyrinogen III created by the bacteria is responsible for the characteristic coral-red fluorescence under Wood's lamp.

Answer 180

►C This child has eczema herpeticum, a cutaneous infection with HSV which occurs in patients with pre-existing skin disorders such as atopic dermatitis. It begins as clusters of umbilicated and hemorrhagic vesicles in areas of abnormal skin. Lesions spread rapidly but can respond quickly to antiviral treatment. Children with underlying AD who come into frequent contact with an individual with orolabial HSV may have recurrent outbreaks of eczema herpeticum.

Answer 181

►D Erythema infectiosum is caused by parvovirus B19 which is a single stranded DNA virus.

Answer 182

►B Blueberry muffin lesions can be seen in the setting of prenatal infections (e.g. TORCH), severe anemia (e.g. Hemolytic Disease of the newborn) and neoplastic diseases (e.g. rhabdomyosarcoma). It is not associated with the Klippel-Trenaunay-Weber syndrome.

Answer 183

►B B. henselae is the cause of cat-scratch disease. Humans are infected by a cat bite or scratch, while the cat flea is responsible for cat to cat transmission.

Answer 184

►D The face is the most common location for Herpes Gladiatorum.

Answer 185

►D Strongyloides stercoralis has a very low prevalence in societies where fecal contamination of soil or water is rare. It is a very rare infection in developed economies and most common in tropical climates. Strongyloides stercoralis causes morphologically variable skin lesions. Rarely, a petechial purpuric eruption which resembles multiple thumbprints may initially present over the periumbilical area. Later on it may involve the whole abdomen, thighs, legs and arms. The petechial purpuric skin lesions in disseminated strongyloidiasis are due to damage to the blood vessels caused by larval migration.

Answer 186

►E Perinatally acquired neonatal herpes disease can present in three different, occasionally overlapping, forms: 1. skin, eyes, and mouth; 2. CNS; and 3. Disseminated, causing encephalitis, hepatitis, pneumonia, and coagulopathy.

Answer 187

►A The measles virus is an RNA virus belonging to the Paramyxovirus family.

Answer 188

►A Leprosy is caused by infections to Mycobacterium leprae. It is a acid fast bacilli. In tuberculoid leprosy, Th1 cytokines (IL-2, IFN-gamma) are upregulated. Clinically, patients have few, wellcircumscribed anesthetic plaques.

Answer 189

►C Rhinoscleroma is caused by Klebsiella rhinoscleromatis, a gram negative rod that causes a chronic granulomatous infection of the upper respiratory tract. It is predominantly seen in Mexico, Central and South America. The histologic hallmark is the Mikulicz cell, a large histiocyte that contains the bacteria in its cytoplasm. Rhinosporidiosis is not an intracellular bacteria, but an extracellular fungi caused by Rhinosporidium seeberi mainly seen in India, Sri Lanka and occasionally the southeastern United States. Extremely large endospores are present in tissue. The other listed organisms are intracellular pathogens but do not have the Mikulicz cell as a feature of infection.

Answer 190

►B The clinical description is that of rickettsialpox, which is caused by R. akari and spread by liponyssoides sanguineus - the house mouse mite.

Answer 191

►A Thrombotic thrombocytopenic purpura has been reported with high doses of valcyclovir in immunosuppressed patients.

Answer 192

►B Bipolar, safety pin-shaped intracytoplasmic inclusions on Giemsa stain - known as Donovan bodies - are diagnostic of granuloma inguinale.

Answer 193

►A Warts are common cutaneous lesions caused by the various human papilloma virus subtypes. Flat warts are commonly caused by HPV subtypes 3, 10, 28, and 41. Sun exposure has been implicated as a potential factor in the formation of flat warts.

Answer 194

►A Leishmaniasis should be cultured in Novy-MacNeal Nicolle (NNN) medium. Sodium stibogluconate is the treatment for cutaneous Leishmaniasis. FTA-ABS and ELISA are used to diagnose syphilis.

Answer 195

►B Doxycycline is the usual treatment for erythema migrans in adults in the absence of neurologic or cardiovascular complications. In children less than 8, all tetracyclines are relatively contraindicated because of they can cause tooth discoloration. Therefore amoxicillin should be used as the first line therapy for children less than 8. Note: Changes have been made to the treatment of RMSF. Children of any age should be treated with doxycycline for that disease.

Answer 196

►A Gonococcemia is caused by Neisseria gonorrhoeae. The clinical features are fevers, chills, arthralgias, malaise with hemorrhagic vesiculopustules with erythematous base on palms, soles and over joints.

Answer 197

►A Rat-bite fever is also called Haverhill Fever. It is caused by Streptobacillus moniliformis and is acquired from infected rodents or by touching or eating contaminated food. The signs and symptoms are nonspecific, but the diagnosis can be suspected based on history. Treatment is with penicillin.

Answer 198

►A Seabather?s eruption characteristically involves areas covered by swimwear, as a result of coelenterate larvae becoming trapped underneath bathing suits. The causative organisms are larval forms of Edwardsiella lineata (sea anemone) and Linuche unquiculata (thimble jellyfish).

Answer 199

►A Bacillus anthracis is responsible for causing Anthrax. Anthrax of the skin is characterized by a painless edematous nodule which rapidly degenerates into an eschar. B. anthracis has 3 virulence factors: a polyglutamate acid capsule which inhibits phagocytosis of the bacteria, edema toxin (edema factor and protective factor) which results in edema secondary to induction of cAMP pathway, and lethal toxin (lethal factor and protective factor) which leads to shock and death via increasing TNFalpha activity.

Answer 200

►C This patient has Ramsay Hunt Syndrome, herpes zoster infection of the geniculate ganglion. Vesicles can be seen on the tympanic membrane and the external ear. Symptoms include ipsilateral facial paralysis, tinnitus, or other auditory symptoms. Treatment is with acyclovir and systemic corticosteroids.

Answer 201

►A Scrofuloderma is a tuberculous or nontuberculous mycobacterial infection affecting children and young adults, representing direct extension of tuberculosis into the skin from underlying structures such as lymph nodes, bone, or lung. It most commonly presents as a neck abscess secondary to a tuberculosis infection of the cervical lymph nodes. It is manifested by the development of painless subcutaneous swellings that evolve into cold abscesses, multiple ulcers, and draining sinus tracts. The diagnosis is based on positive Mantoux test/PPD test, histologic features of caseating granulomatous inflammation, culture, and favorable response to anti tuberculosis therapy.

Answer 202

►A A painless chancre with an indurated border is characteristic of primary syphilis. Associated painless lymphadenopathy ("buboes") is also a common feature.

Answer 203

►C Causes of angiomatous papulonodules arising in immunocompromised patients include Kaposi‟s sarcoma, bacillary angiomatosis, and verruga peruana, as well as pyogenic granulomas and cherry angiomas. Bartonella, a gram negative bacillus, appears as faint purple-blue granular dermal deposits on routine H&E-stained sections. These deposits appear black upon WarthinStarry staining. Prominent endothelial cells may also be seen. Both B. henselae and B. quintana have been implicated in the pathogenesis of bacillary angiomatosus, while B. bacilliformis is the causative agent in verruga peruana (as well as Bartonellosis). Erythromycin is the first -line treatment for bacillary angiomatosus, while fluoroquinolones plus a tetracycline are the first-line agents for treatment of verruga peruana.

Answer 204

►D B. quintana or B. henselae are both causative organisms for bacillary angiomatosis.

Answer 205

►B Dengue fever is caused by an Arbovirus and transmitted by the mosquito, Aedes aegypti and may cause Dengue Shock Syndrome and Dengue Hemorrhagic Fever. The infection starts with sudden onset of high fever, backache, retroorbital pain, bone and joint pain, depression and malaise. The disease is also called "break-bone fever." One to seven days after onset of fever, rash presents characteristically starting on the dorsum and hands and feet spreading to limbs and torso. The eruption may become confluent with small, round islands of sparing, the so called "white islands in a sea of red." Treatment is generally supportive as no antivirals are effective.

Answer 206

►D Acrodermatitis chronica atrophicans, also known as primary diffuse atrophy, is characterized by the appearance on the extremities of diffuse reddish or bluish red, paper-thin skin allowing the blood vessels to easily be seen beneath the skin. It is caused by Borrelia afzelii and is tick transmitted by Ixodes ricinus. It is seen almost exclusively in Europe.

Answer 207

►A Purpura fulminans is causes by group A streptococcal infection. Clinically there are hemorrhagic infarction of the skin caused by disseminated intravascular coagulation. One can see symmetric large ecchymotic areas with irregular ("geographic") borders on extremities, ears and nose most commonly.

Answer 208

►B A significant number of people are asymptomatic for HSV infection but are seropositive for anti HSV antibodies. Lumbosacral HSV occurs in about 10% of HSV infections and is more common in older age groups. In some cases, this may be the “first” presentation of HSV that the patient is aware of. Shingles would be a reasonable consideration for the differential diagnosis and a direct immunofluorescence scraping and viral culture would confirm that this typical presentation of HSV actually is. It is possible that the patient is lying or that he has early Alzheimer‟s disease, but less likely. EBV does not present in this manner.

Answer 209

►A Papular-purpuric gloves and socks syndrome is characterized by pruritus, erythema, and edema of the hands and feet, primarily in teenagers and young adults. Parvovirus B19 is classically associated with this eruption. While all of the viruses listed as answer choices have been associated with this syndrome; Epstein-Barr virus is the best answer choice.

Answer 210

►A Lichen planus presents a wide variety of cutaneous morphologies that share common histologic findings of a lichenoid lymphocytic infiltrate, basal vacuolization, and dyskeratotic keratinocytes. The form of lichen planus most strongly associated with Hepatitis C virus infection is mucosal ulcerative lichen planus.

Answer 211

►B The human body louse is the implicated Trench fever, epidemic typhus, and relapsing fever. Trench fever usually affects alcoholic men and is manifested by fevers. Treatment is with ceftriaxone, erythromycin, or doxycycline. Epidemic typhus is manifested by fevers, chills, malaise, and a pink macular eruption beginning in the axilla and trunk. Treatment is with tetracycline or chloramphenicol. Relapsing fever is manifested by paroxysmal fevers, headache, lymphocytoma, and erythematous/petechial macules on trunk/extremities. Treatment is with doxycycline.

Answer 212

►C Staphylococcal scalded skin syndrome: Lesions extend far beyond areas of actual staphylococcal infection, by action of the epidermolytic exotoxin elaborated by the staphylococcus in remote sites. Usually the staphylococci are present at a distant focus such as the parynx, nose ear, or conjuctiva. If cultures are taken they should be obtained fromthe mucous membranes because the skin erythema and desquamation is due to the distant effects of the exfoliative toxin, unlike the sitaution in bullous impetigo, where S. aureus is present in the lesions. Epidermal changes are produced by exfoliative toxins of Staphylococcus. Inital event is usually a localized Staph infection. Prognosis is good in children with low mortality when anitbiotics are administered earyl. Cell necrosis does not occur in SSS as it does in toxic epidermal necrolysis.

Answer 213

►C Milker‟s nodule is caused by paravaccinia virus, a poxvirus of the genus Parapoxvirus. It is transmitted to humans from infected cows.

Answer 214

►C Human herpes virus 8 is a double stranded DNA virus. It is thought to be pathogenic in Kaposi”s sarcoma, primary effusion lymphoma, and Castleman”s disease. Primary effusion lymphoma is a rare B-cell lymphoma seen predominantly in patients with AIDS.

Answer 215

►C Clarithromycin is not part of the WHO recommendations for the treatment of multibacillary leprosy.

Answer 216

►C Granuloma inguinale is caused by an infection of Klebsiella granulomatis. It is a granulomatous skin disease of the genitals caused by sexual transmission. It is a gram negative rod that is similar to the Enterobacteriaceae. It is a smll, raised papule or subcutaneous nodule that rapidly ulcerates, rarely with lymphadenopathy. It is not self healing and spreads by radial extension. Hemophilis ducreyi is the cause of chancroid, Chlamydia trachomatis causes Lymphogranuloma Venereum, Treponema pertenue causes Yaws and T. pallidum is the cause of syphilis.

Answer 217

►A Tularemia is caused by Francisella tularensis. It is most likely caused by infected rabbits seen in hunters. There are other forms such as glandular, chancriform, oculoglandular, pulmonary, oropharyngeal and meningeal. The treatment is streptomycin.

Answer 218

►D The definition of dissemianted herpes zoster is at least 20 vesicles seen outside of the primarily affected dermatome. The other option choices are distractors.

Answer 219

►D Necrotizing fasciitis is a rapidly advancing acute necrotizing infection that may follow trauma, surgery, or occur spontaneously. It is associated with systemic toxicity and high mortality rat e. Clinically, erythema, edema, and edema progresses to dusky cyanosis, blistering and necrosis. Many virulent bacteria have been culturesd including Pseudomonas, Bacteroides, streptococci, staphylococcus, enterococci, and clostridium. Both aerobic and anaerobic cultures should be taken. Mycobacterium is not associated with necrotizing fasciitis.

Answer 220

►C M. leprae cannot be grown in media or cell culture. It has been grown in mice footpads and in armadillos. Humans are the only natural host. It is endemic in the tropics and found worldwide. The Lowenstein-Jensen medium is used to culture mycobacteria most commonly. Neisseria gonorrheae is grown on chocolate agar in 10% CO2. Agar supplemented with heme (x-factor) and nicotinamide (v-factor) is needed for Hemophilus influenzae cultures. Sheep‟s blood agar is useful for identifying hemolytic strains of streptococcus and staphylococcus.

Answer 221

►A Paucibacillary leprosy is characterized by three or fewer anesthetic and anhidrotic lesions. This form of leprosy develops when the body mounts a Th1 cytokine profile leading to rare bacilli found in the lesions. The WHO recommends treatment of paucibacillary leprosy with dapsone 100 mg daily for 6 months and rifampin 600 mg monthly for 6 months.

Answer 222

►B Hutchinson”s teeth (widely-spaced, peg-shaped upper incisors) are a seen in Late Congenital Syphilis (> 2 years of age).

Answer 223

►A HIV/AIDS patients are afflicted with a wide variety of opportunistic pathogens. The spectrum of infectious diseases can be used to predict a patient's CD4 helper T cell count. Molluscum contagiosum is usually not seen until a patient's CD4 count drops below 100.

Answer 224

►A Swimmers itch also known as Clam Digger's itch is caused by the cercarial forms flatworms of the family Schistosomatidae. The mode of infection is penetration of skin while bathing in infested fresh or salt water in Northern United States and Canada. The clinical characteristics are pruritic papules and papulovesicles on uncovered skin.

Answer 225

►C Clindamycin is considered 1st line treatment of streptococcal toxic shock syndrome, as it inhibits secretion of the exotoxin.

Answer 226

►A Roseola infantum is also known as exanthem subitum or sixth disease. It is seen in infants ages 6-36 months, and is characterized by the signs and symptoms as described. The syndrome is caused by Human Herpes Virus 6.

Answer 227

►B Xenopsylla cheopis along with Ctenocephalides felis are fleas that transmit R. typhi, the organism responsible for murine or endemic typhus. The body louse or Pediculus humanus corporis transmits Rickettsia prowasekii the organism responsible for epidemic typhus. Scrub typhus is caused by R. tsutsugamushi and is transmitted by chiggers or trombiculid mite larvae.

Answer 228

►A The lesions of secondary syphilis are often diffusely distributed due to spirochetemia. Papulosquamous lesions are characteristic, and the presence of constitutional symptoms such as fever, fatigue, headaches, and bone pain may help distinguish secondary syphilis from pityriasis rosea. Other lesions of secondary syphilis include ˜moth-eaten” alopecia, mucous patches, split papules, and condyloma lata. The mucocutaneous manifestations of secondary syphilis typically occur 3-12 weeks after the appearance of the chancre and last 4-12 weeks.

Answer 229

►A Molluscum contagiosum virus, like other viral and bacterial pathogens, attempts to exploit the host immune system to avoid destruction. In this case, molluscum contagiosum virus usesIL-18 binding protein, which blocks the host helper T (Th1) response by reducing local IFN-gamma production.

Answer 230

►A Verruga Peruana is caused by infection with B. bacilliformis, which is transmitted by the sandfly, Lutzomyia verrucarum.

Answer 231

►B Epidemic typhus is caused by infection with R. prowazekii.

Answer 232

►C Dracunculiasis, which is caused by Dracunculus medinensis, is acquired by ingestion of copepod- infested water.

Answer 233

►B Eikenella corrodens is a member of normal oral flora, that is commonly the cause of human bite and fist fight infections. Pasturella multocida is a common organism found in dog and cat bites. Staph and Strep could be the right answers for a cellulitis, but with this history are not the correct choices. Baceriodes fragilis is found in normal bowel flora.

Answer 234

►D All of the listed options except condylomata lata are manifestations of tertiary syphilis, which does not manifest for years after the initial infection. Secondary syphilis presents 2 -6 months following infection. Condylomata lata are moist, flat and smooth. Do not confuse them with Condyloma accuminatum which are usually dry, cauliflower-like projections on the genitalia.

Answer 235

►B Secondary syphilis is characterized by ham-colored macules on the palms and soles, condyloma lata, and "moth-eaten" alopecia, in addition to mucous patches and split papules. It typically lasts 4-12 weeks.

Answer 236

►E Foscarnet directly inhibits viral DNA polymerase (without requiring phosphorylation by TK) and is therefore effective in acyclovir-resistant HSV infections. Cidofovir can also be used.

Answer 237

►A Herpes simlex virus is characterized by Cowdry type A bodies on histopathology. They appear as sharply demarcated eosinophilic structures separated by a clear halo from a basophilic rim of the infected cell's marginated nuclear chromatin. Cowdry B bodies may be seen in polio infections.

Answer 238

►A West African sleeping sickness is caused by Trypanosoma bruci gambiense and leads to acute illness with rapid fatal course and pronounced posterior cervical lymphadenopathy (Winterbottom's sign). East African sleeping sickness is due to T. brucei rhodesiense (east like rhode island) and is more chronic . American trypanosomiasis, or Chagas disease, features unilateral conjunctivitis and edema of the face (Romana's sign) and heart and gastrointestinal sequelae. Schistomsomiasis causes swimmer's itch, while sparaganosis from ingestion of Spirometra leads to painful edematous lumps.

Answer 239

►B Vibrio parahemolyticus is a cause of gastroenteritis after consuming contaminated seafood or shellfish. V. vulnificus infection occurs in cuts/wounds that contact contaminated seawater or marine organisms. M. marinum occurs after injury in an aquatic environment such as a fish tank or swimming pool. Lesions typically occur on hands, elbows or knees and are characterized by painless inflammatory nodules that may ulcerate and may occur in a sporotrichoid pattern. E. rhusiopathiae infection occurs after injuries in fishermen, butchers or those handling raw meat. Initially there is burning pain at the inoculation site followed by a gradually enlarging purple plaque with well defined margins. T. carateum is the cause of Pinta.

Answer 240

►A Toxic Shock Syndrome is characterized by fever, hypotension, and a generalized scarlatiniform eruption followed by desquamation. Menstrual-associated TSS is generally driven by Staphylococcus aureus, which released Toxic Shock Syndrome toxin 1. In nonmenstrual cases, however, Enterotoxins B>C are more commonly implicated, although TSST-1 has also been associated. Exfoliative toxins A and B are involved in bullous impetigo, and edema toxin and lethal factor are involved in Bacillus anthracis infections.

Answer 241

►A Symptomatic thrombocytopenia, while rare, has been associated with acute varicella-zoster virus infection.

Answer 242

►A Herpes gladiatorum is most commonly seen on the lateral neck, lateral face, and forearm, areas which most commonly contact a competing wrestler or the wrestling mat.

Answer 243

►A Herpes zoster vaccine is a live attenuated vaccine and can help reduce the incidence of herpes zoster and decrease the chance of post-herpetic neuralgia.

Answer 244

►E Anthrax is caused by Bacillus anthracis, which is a gram-positive spore-forming rod.

Answer 245

►C The nature of the maternal infection (primary versus recurrent) is the most important predictor of maternal-fetal transmission of HSV-2. In mothers with a primary infection, the risk of transmission is 25-50%. In mothers experiencing a recurrent infection, the risk is 2-5%

Answer 246

►B Orf is caused by orf virus (OV), a poxvirus of the genus Parapoxvirus.

Answer 247

►A Cat-scratch disease is caused by Bartonella henselae, which is spread among cats by fleas. The hallmark of the disease is unilateral and regional lymphadenopathy. The treatment of choice for cat- scratch disease is Azithromycin.

Answer 248

►D Bullous impetigo is caused primarily by staphylococcus aureus phage type 71. This bacteria produces exfoliative toxin A binds to desmoglein 1 and produces produces the blisters characteristic of bullous impetigo.

Answer 249

►E Rickettsia are short, gram-negative rods which are strict intracellular parasites. The bacteria is transmitted via tick which much be attached for more than 6 hours. The Weil-Felix test exploits cross-reactivity between the Proteus vulgaris antigen and RIckettsia.

Answer 250

►C The image shows Pitted keratolysis. It is a non-inflammatory bacterial infection caused by microcolonies of Micrococcus sedentarius or Corynebacterium species that produce a specific proteolytic enzyme which digests the stratum corneum. It consists of small crater-like depressions in the stratum corneum, and usually appear on the weight-bearing regions of the soles of the feet, but can occur in other non weight-bearing areas as shown in image. This was confirmed with shave biopsy of epidermis that is step-sectioned and stained with methenamine silver as this is found to be more helpful than a punch biopsy. The disease usually goes unnoticed by patients and is most often an incidental finding. Hyperhidrosis and malodor of the skin are very common findings. Corynebacterium minutissimum is the causative agent for erythrasma, and Corynebacterium tenius causes trichomycosis Axillaris.

Answer 251

►C Scarlet fever is primarily a disease of children with most cases occurring between the ages of 1 and 10 years of age. Streptococcus pyogenes is the causative organism. It produces the streptococcus pyrogenic exotoxin which elicits the cutaneous manifestations by enhancing delayed type hypersensitivity to streptococcal products. Clinical findings include fever, sore throat, headache, chills, sandpaper rash on the trunks, strawberry tongue, and Pastia‟s lines (linear petechial streaks found in flexural locations).

Answer 252

►A The most common cause of erythema multiforme (EM) is herpes simplex virus, which may not be active at the time of the EM eruption. Patients with recurrent EM are typically treated with acyclovir or valacyclovir. Mycoplasma pneumonia is a cause of EM, but is not the most common. Amoxicillin, ibuprofen, and cytomegalovirus may cause EM, but are not as common.

Answer 253

►A Hansen's disease (aka Leprosy) is a chronic granulomatous disease principally affecting the skin and peripheral nervous system, caused by Mycobacterium leprae. Lepromatous leprosy is described where there is low immune response to the bacteria. The areas most commonly affected are the superficial peripheral nerves, skin, mucous membranes of the upper respiratory tract, anterior chamber of the eyes, and testes. These areas tend to be cool parts of the body. Tissue damage depends on the degree to which cell-mediated immunity is expressed, the type and extent of bacillary spread and multiplication, the appearance of tissue-damaging immunologic complications (ie, lepra reactions), and the development of nerve damage and its sequelae. The late complications of lepromatous leprosy include madarosis = loss of eyebrows, leonine facies, stockin gglove neuropathy and lagopthalmosis.

Answer 254

►A Lupus vulgaris spreads from hematogenous, lymphatic, or contiguous spread from distant site of tuberculous infection. It is sensitizes the host with moderate to high immunity. It is pauci bacillarry. It also involved the head/neck in 90% of cases.

Answer 255

►C Rocky Mountain spotted fever is caused by Rickettsia rickettsii. Human monicytic ehrlichiosis is caused by Ehrlichia chaffeensis. Colorado tick fever is caused by Reoviiridae. Boutonneuse fever is caused by Rickettsia conorii. Q fever is caused by Coxiella burnetti.

Answer 256

►C Scrofuloderma is the result of contiguous spread onto skin from an underlying focus of tuberculous infection. This typically occurs in a sensitized host with low immunity.

Answer 257

►C The FTA-ABS test measures the presence of antibodies in the patient‟s serum to the syphilis antigens, either on spirochetes or on attached red blood cells. The RPR and VDRL are non specific tests that rely on cross-reactive anti-phospholipid antibodies. Darkfield microscopy is not specific to T. pallidum, but will identify other spirochetes also. A CBC would not be specific for T. pallidum.

Answer 258

►D The risk of developing herpes zoster following stem cell transplantation for leukemia is quite high, approaching 70% in some studies.

Answer 259

►B HSV related erythema multiforme has been associated with an increased frequency of HLA-B15.

Answer 260

►E Heck‟s disease (focal epithelial hyperplasia) is caused by HPV 13 and 32 infections. These lesions are multiple circumscribed papules on the oral mucosa that may resemble oral condyloma. They are not pre-cancerous. HPV-1 is associated with plantar warts, while HPV-3 is associated with flat warts. HPV-7 cause “butcher‟s warts” and are believed to be acquired from handling meat, poultry and fish.

Answer 261

►E No therapy is needed, since orf is usually a benign, self-resolving infection. Orf is caused by a parapoxvirus, often associated with sheep and goats. The infection undergoes 6 different stages of evolution: the papular, target, acute, regenerative, papillomatous, and regressive stages.

Answer 262

►A This patient has rhinoscleroma, which looks like hypertrophic plaques on external nares. The causative organism is Klebsiella pneumoniae rhinoscleromatis. Mikulicz cells are seen on histopathology and the treatment is ciprofloxacin.

Answer 263

►B Bacillary angiomatosis is caused by both B. henselae and B. quintana. The vector is unknown and the treatment is erythromycin and doxycycline.

Answer 264

►B The Lowenstein-Jensen medium is used to culture mycobacteria most commonly. Neisseria gonorrheae is be grown on chocolate agar in 10% CO2. Thayer “Martin, Martin-Lewis or New York City medium also allow for N. gonorrheae growth. Agar supplemented with heme (x factor) and nicotinamide (v-factor) is needed for Hemophilus influenzae cultures. Sheep”s blood agar is useful for identifying hemolytic strains of streptococcus and staphylococcus.

Answer 265

►A Herpangina is caused by Group A coxsackievirus.

Answer 266

►C Streptococcus iniae most commonly causes bacteremic cellulitis of the hand in persons who have recently handled fresh fish. S. iniae is a fish pathogen that causes sporadic infection in tilapia, yellowtail, rainbow trout, and coho salmon. Treatment of choice is with penicillin antibiotics.

Answer 267

►B A painless ulcer in an HIV patient is most likely a syphilitic chancre. The treatment of choice is benzathine penicillin G in patients without a penicillin allergy. Alternative agents in allergic patients include doxycycline, tetracycline, erythromycin, and ceftriaxone. Valacyclovir would be the treatment of choice for genital herpes, which is typically painful. Azithromycin in a single 1 g oral dose is effective for chancroid, which is painful.

Answer 268

►E Anthrax can present in three different clinical forms: cutaneous, inhalational, and gastrointestinal. The cutaneous form appears as a painless vesicle that later forms an eschar (malignant pustule). The cutaneous form has a mortality rate of less than 1% if treated an up to 20% if untreated.

Answer 269

►A Leprosy is caused by mycobacterium leprae. Armadillos are a source of nonhuman source for leprosy. They are also transmitted from human to human most likely from respiratory secretions.

Answer 270

►A The organisms that are responsible for old world Leishmaniasis are L. major, L. tropica, L. aethiopica, L. infantum, L. donovani. Those that are responsible for new world Leishmaniasis are in south and central America which are L. mexicana, L. braziliensis, and L. amazonensis.

Answer 271

►E The human papilloma virus is a member of the Papovavirus family, a double-stranded DNA virus. HPV, type 6 has been implicated in giant conduloma of Buschke and Lowenstein and anogenital condyloma.

Answer 272

►D Streptococcus iniae has been demonstrated to cause hand cellulitis from puncture wounds sustained form the dorsal fin, fish bone or knife of usually a tilapia. Treatment with PCN is curative. Group A Streptococci are the most common cause of perianal dermatitis. Many different bacteria have been implicated in necrotizing fasciitis. Bullous impetigo is most frequently caused by phage type 71 S. aureus or a related group 2 phage type. Group B streptococcus is most often responsible for perineal erysipelas in postpartum women.

Answer 273

►A Treponema carateum is the cause of Pinta which is primarily transmitted by direct contact. Occasional insect vectors have also been implicated, but sexual contact is not the primary cause of spread. The other options (C. trachomatis, H. ducreyi, C. granulomatis and T. pallidum) are all venereal diseases.

Answer 274

►A The patient has lymphogranuloma venereum that is caused by Chlamydia trachomatis L1, L2, L3. It is a painless soft erosion that heals spontaneously. Serologic diagnosis is by complement fixation test. The treatment is doxycycline.

Answer 275

►A This patient has lupus vulgaris, a pauci-bacillary manifestation of tuberculosis infection. Lesions occur in sensitized patients with a moderate to high immune response and are due to hematogenous, lymphatic, or contiguous spread from a distant site of infection. Lesions typically occur on the head and neck. "Apple jelly" color on diascopy is described in lupus vulgaris, but can also be seen in cutaneous lesions of sarcoidosis.

Answer 276

►A This patient has cryoglobulinemia. This is associated with HCV infection. Approximately 80% of cases of mixed cryoglobulinemia are associated with HCV infection.

Answer 277

►A The ophthalmic branch of the trigeminal branch is involved in ophthalmic zoster. This presentation accounts for 10-15% of all cases of VZV. The other nerve branches listed are not involved in ophthalmic zoster.

Answer 278

►E Hand-Foot-and-Mouth disease is caused by coxsackievirus A16. Group A coxsackievirus infection is also associated with herpangina.

Answer 279

►A The most common associated autoimmune disorder is autoimmune thyroiditis. The others can be associated with hepatitis C extra systemic manifestation but is not as common.

Answer 280

►A This patient above has classic kaposi's sarcoma. It is caused by HHV-8 that causes the abnormal vascular proliferation associated with this condition. Classic KS is seen in middle aged men from southern-eastern european heritage.

Answer 281

►E Anthrax is a gram positive, spore-forming rod. Meningococcemia, gonorrhea, Glanders, and Meloioidosis are all gram negative. Infection with anthrax initially begins after skin onoculation or may follow after ingestion or inhalation of spores. Cutaneous anthrax initially begins as a localized infection and subsequently evolves to toxemia. It appears as a painless papule that ay later become hemorrhagic or nerotic. It produces two exotoxins: edema toxin and lethal toxin. Edema toxin is comprised of edema factor and protective antigen. Lethal toxin is composed of lethal factor and protective antigen.

Answer 282

►A The human body louse (Pediculus humanus corporis)is the vector of Trench Fever, Epidemic Typhus, and Relapsing Fever.

Answer 283

►C Brucella species which cause Brucellosis are gram negative rods. Brucellosis, aka undulant fever, is characterized by an acute febrile illness with headache and joint pain. CNS and cardiac manifestations can also occur. It is acquired by contact with infected animals or contaminated dairy products. Treatment is with doxycycline and rifampin.

Answer 284

►B Secondary syphillis is caused by the spirochete, T. pallidum. Penicillin is the treatment of choice for secondary syphillis. In penicillin allergic individuals, doxycyline may be used. Treatment for neurosyphilis, congenital syphilis and syphilis in pregnant women is desensitization to penicillin and then treatment with pcn.

Answer 285

►D Inguinal adenopathy with fluctuant, tender nodes above and below Poupart”s ligament - referred to as “groove sign” - is a characteristic clinical feature of lymphogranuloma venereum.

Answer 286

►B Purpura fulminans is an oftentimes dramatic presentation of large ecchymotic areas of the skin, favoring acral sites including the extremities, ears, and nose. The underlying pathophysiology is hemorrhagic infarction of the skin due to disseminated intravascular coagulation. Meningococcal infection is the leading underlying infection associated with sepsis and purpura fulminans. When Kids develop purpura fulminans after an infection the most common cause is group A Strep.

Answer 287

►A Leishmaniasis recidivans is a type of Old World leishmaniasis. Clinically, it appears as a red papule covered with white scale. On diascopy, it has a characteristic apple jelly color.

Answer 288

►C Neisseria gonorrheae should be grown on chocolate agar in 10% CO2. Thayer”Martin, Martin- Lewis or New York City medium also allow for N. gonorrheae growth. Agar supplemented with heme (x-factor) and nicotinamide (v-factor) is needed for Hemophilus influenzae cultures. Darkfield microscopy is helpful in diagnosing infections with Treponema pallidum (syphilis). Sheep”s blood agar is useful for identifying hemolytic strains of streptococcus and staphylococcus.

Answer 289

►A Louse-born relapsing fever is caused by Borrelia recurrentis. It is seen in Africa and South America, and is spread by the human body louse (Pediculus humanus). Symptoms include paroxysmal fevers, headache, myalgias, and petechial macules on trunk and extremities. Borrelia burgdorferi causes Lyme disease; Borrelia duttonii and Borrelia hermsii cause tick-born Relapsing Fever; Streptobacillus moniliformis causes Rat-bite fever.

Answer 290

►E In the setting of pregnancy, amoxicillin is the treatment of choice for Lyme Disease since doxycycline is contraindicated.

Answer 291

►E HPV 60 infection leads to a particular type of plantar wart called the ridged wart. HPV 1 leads to plantar warts and myrmecia. HPV 7 causes butcher's warts. HPV 11 along with 6 causes anogenital condyloma and giant condyloma of Bucke and Lowenstein (verrucous carcinoma). HPV 18 causes anogenital dysplasia and neoplasms.

Answer 292

►D Zoster usually resolves without sequelae in children and young adults with intact immune systems. However, the pain, cutaneous eruption and complications of zoster become more severe with increasing age and immune compromise. Complications of zoster include post-herpetic neuralgia (PHN), secondary bacterial infection, scarring, ophthalmic zoster, Ramsay-Hunt syndrome, meningoencephalitis, motor paralysis, pneumonitis and hepatitis.

Answer 293

►A Of the answer choices, molluscum contagiosum is the only pox virus. Pediculosis capitis, the cause of lice, and sarcoptes scabei, the cause of scabies are not viruses. Herpes simplex virus is a herpes virus and HIV is a lentivirus.

Answer 294

►B LGV is a sexually transmitted disease that is characterized by suppurative inguinal adenitis with matted lymph nodes, inguinal bubo with secondary ulceration, and constitutional symptoms. It is caused by Chlamydia trachomatis serotypes L1, L2, and L3. First line treatment is doxycycline 100mg bid for 3 weeks as well as treating the sexual partners. Gamma-Favre bodies are found in histiocytes in LGV.

Answer 295

►B Group B streptococcus is S. agalactae, commonly isolated from normal vaginal mucosa. In neonates, impetigo caused by group B streptococci may develop. Listeria monocytogenes is a small, gram-positive organism that may present as petechial, papular or pustular eruptions in acutely ill infants, usually those that were meconium stained at birth. The usual cause of ecthyma is Group A streptococcus, though other organisms can occasionally cause similar cutaneous infections. Group D streptococcus/Lancefield type O organisms are enterococci. S. aureus can secondarily infect a lesion of ecthyma but is not the usual cause of this condition.

Answer 296

►C Congenital CMV is the leading infectious cause of deafness and mental retardation in the U.S.

Answer 297

►A Molluscum contagiosum is a common opportunistic infection of HIV patients. Lesions can be seen anywhere, but the most common locations are on the face and genitalia.

Answer 298

►B This condition described is trichomycosis axillaris. Despite the “mycosis” in the name, it is not fungal in etiology, but caused by C. tenius. Treatment is topical erythromycin or simply shaving the infected hairs. The other listed organisms do not cause this type of infection.

Answer 299

►D Recurrent erythema multiforme (EM minor) is usually caused by recurrent herpes simplex, most commonly HSV-1 orolabial disease. This is more correctly now called herpes-associated erythema multiforme(HAEM) and has been more commonly associated with people with HLA type B15.

Answer 300

►D Staphylococcal scalded skin syndrome is described in the question. This is predominantly a disease of young children, < 5 years old. The mortality is low in children, but in adults it exceeds 50% due to sepsis and electrolyte and fluid imbalance. NSAID use may predispose patients to a poorer outcome. Normal renal function and immune system are helpful, but do not predict the best outcome.

Answer 301

►E Group A streptococcus and Neisseria meningitidis are the leading bacterial causes of purpura fulminans.

Answer 302

►A M. Kansasii, M. marinum, and M. simiae are photochromogens. They form pigment when exposed to light.

Answer 303

►D ELISA - Captia (IgM) EIA is 100% specific for treponemes and is the serology of choice in early primary or congenital syphilis because it is the first to become reactive. FTA-Abs is the most sensitive serologic test for syphilis and MTA-TP stays positive for life (but is less sensitive than FTA-ABs during early disease). The two nontreponemal tests for syphilis include VDRL and RPR. VDRL is used to follow response to therapy.

Answer 304

►B The presentation of a suppurative nodule discharging sulfur granules on the jawline of a patient with poor oral hygeine is characteristic of actinomycosis - caused by the anaerobic gram-positive rod, Actinomyces israelii. This differs from Actinomycetoma, which is a slowly progressive subcutaneous infection characterized by tumefaction, draining sinuses, and an exudate containing grains on microscopy. Unlike Eumycetomas - caused by fungi - Actinomycetomas are bacterial infections. The foot is the most common location, followed by the thoracic area.

Answer 305

►A Staph scaled skin syndrome is caused by exfoliative toxins A and B (ET-A and ET-B) produced by S. aureus (phage group II, types 71 and 55 most common). Histopathology of the skin shows superficial intraepidermal splitting without epidermal necrosis with very few inflammatory cells. Desmoglein 1 is the specific receptor for exfoliative toxin A cleavage. Desmoglein 1 is the antigen targeted in Fogo selvagem, the vector for which is the black fly. Bullous impetigo is caused by Staph and is a subgranular blister with bacteria and neutrophils on histopahtology. Pemphigoid and pemphigus would be less likely in a child.

Answer 306

►A Bartonella hensalae is the causative agent of bacillary angiomatosis. The differential diagnosis of bacillary angiomatosis may include pyogenic granulomas and Kaposi's sarcoma. The treatment of choice is erythromycin.

Answer 307

►B Ecthyma is a deep or ulcerative type of pyoderma commonly seen on the lower extremities and buttocks and caused most often by GABHS, in addition to staphyloccous aureus which also can be involved in the infection. Ecthyma can present as small punched-out ulcers or a deep spreading ulcerative process. The disorder begins in the same manner as impetigo, often following infected insect bites or minor trauma, but penetrates through the epidermis to produce a shallow ulcer. The initial lesion is a vesiculopustule with an erythematous base and firmly adherent crust. Removal of the crust reveals a lesion deeper than that seen in impetigo, with an underlying saucer-shaped ulcer and raised margin. The lesions are painful and heal slowly over a few weeks, often with scar formation. Ecthyma gangrenosum is a cutaneous finding that may be seen in patients with Pseudomonas aeruginosa bacteremia. Most of the affected individuals have an underlying immunodeficiency (either congenital or acquired) or a history of cancer chemotherapy. Neutropenia may be a risk factor for ecthyma gangrenosum

Answer 308

►B American trypanosomiasis (Chagas‟ disease) is caused by infection with Trypanosoma cruzi via Triatoma arthropod vectors (reduviid bugs) and is prevalent predominantly in Central and South America. Transmission of this protozoal infection may occur following the bite of an infected reduviid bug, who then defecates on human skin after feeding, allowing the metacyclic trypomastigotes entry into the bite wound. Alternatively, infected feces may gain direct entry through mucosal surfaces, including the conjunctivae. When the latter occurs, characteristic unilateral palpebral and periorbital edema ensues, known as “Romana‟s sign.” Entry into the skin may result in a localized plaque of erythema and induration with regional lymphadenopathy, termed a “chagoma.” Other systemic complications resulting from chronic infection include cardiac arrhythmias, congestive heart failure, megacolon, and megaesophagus. Treatment is with nifurtimox or benznidazole.

Answer 309

►C First line treatment of herpes zoster (shingles) is with valacyclovir, acyclovir, or famciclovir. Gabapentin may be used for post-herpetic neuralgia. Cidofovir and ganciclovir are treatment options for cytomegalovirus. Foscarnet is used to treat acyclovir resistant herpes simplex infections.

Answer 310

►D Gardasil is a quadrivalent vaccine containing HPV types 6, 11, 16 and 18. It is approved for females ages 9 to 26. Neither HPV testing nor pap smears are necessary before vaccine administration. It is recommended for the prevention of cervical, vaginal, and vulvar cancers, as well as for genital warts.

Answer 311

►A M. marium is also known as fish tank granuloma. Empiric therapy is suggested with M. marinum infection and the first line treatment is minocycline, #2 is clarithromycin. c

Answer 312

►A African trypanosomas is also known as sleeping sickness and is caused by Trypanosoma brucei and transmitted by the tsetse fly Glossina. It can occasionally have cutaneous manifestations such as chancre and trypanids.

Answer 313

►A Rat-bite fever (Haverhill fever) is caused by Streptobacillus moniliformis.

Answer 314

►C Tularemia is caused by infection with Francisella tularensis - most commonly acquired after contact with infected rabbits (e.g. hunters).

Answer 315

►B This patient most likely has contract Mycobacterium marinum, otherwise known as "fish tank granuloma." On primary isolation M. marinum grows best at 30-33 degrees C in 7-21 days. Unlike Mycobacterium tuberculosis, most strains of M. marinum will not grow at the usual incubation temperature of 37 degrees C. Dimorphic fungi have both yeast and fungal forms: hyphae morphology at 25 degrees C and yeast phase at 37 degrees C.

Answer 316

►D The DNAse B, hyaluronidase or streptolysin O (ASLO) antibodies in serum can be helpful for confirming streptococcal infection in situations where streptococci cannot be isolated. The FTA ABS is used for detecting syphilis, and is the only test that is positive in the first 14 days of infection. U1-RNP is an extractable nuclear antibody which is a marker for Mixed Connective Tissue Disease.

Answer 317

►C The infection depicted is larva migrans or creeping eruption which is caused by Ancylostoma braziliense. This nematode is typically a hookworm of cats and dogs. It migrates at a rate of 2 cm/ day. Larva currens migrates at a rate of 10 cm/day.

Answer 318

►A The question stem describes Ramsay-Hunt syndrome, which is characterized by unilateral vesicles on palate, tongue, earlobe, and eardrum, in association with neurologic symptoms including vertigo, difficulty speaking, difficulty eating, hearing loss, and facial droop. The syndrome is caused by varicella-virus infection of the geniculate ganglion.

Answer 319

►A The presentation described above is that of Tularemia, caused by Francisella tularensis. The most common form of Tularemia is the ulceroglandular form, which is described above. Infected animals, most commonly rabbits, transmit the organism though occasionally tick bites or deer flies may be the vector. Squirrels may be the vector of bubonic plague in endemic areas. The other animals would not cause a syndrome as described.

Answer 320

►C Rickettsial pox is diagnosed by clinical suspicion and confirmatory biopsy, the Weil -Felix test is rarely positive. The other listed Rickettsial diseases will have positive Weil-Felix tests. The Weil- Felix test makes use of the cross-reaction between antigens from the gram-negative Proteus vulgaris species and Rickettsia spp. It is not specific and rising titers in the appropriate clinical presentation is necessary for confirmation. The Proteus antigens OX-K, OX-19 and OX-2 are employed.

Answer 321

►B Rickettsialpox is an acute febrile illness caused by the bacteria Rickettsia akari, a member of the spotted fever group. R. akari is transmitted by the house mouse mite, Liponyssus sangineus. Clinically, patients have an eschar at the inoculation site with a subsequent papulovesicular rash, fevers, headache, chills, diaphoresis, myalgia, and anorexia.

Answer 322

►A Granuloma inguinale is caused by Klebsiella (old name: Calymmatobacterium) granulomatis. The primary lesions are pseudobubo or ulcer. There are four clinical forms: ulcerovegetative, nodular, hypertrophic, and cicatricial. Donovan bodies are seen on microscopy.

Answer 323

►A The usual cause of ecthyma is Group A streptococcus, though other organisms can occasional ly cause similar cutaneous infections. Group B streptococcus is S. agalactae, commonly isolated from normal vaginal mucosa. Infections can be problematic for neonates, but not a frequent cause of ecthyma. Group D streptococcus/Lancefield type O organisms are enterococci. S. aureus can secondarily infect a lesion of ecthyma but is not the usual cause of this condition.

Answer 324

►C Dengue fever also known as "break-bone" fever is characterized by sudden high fever, backache, retro-orbital pain, bone/joint pain, weakness, and malaise. It is caused by an arbovirus (RNA virus) which is transmitted by Aedes aegypti, a species of mosquito.

Answer 325

►D Focal epithelia hyperplasia, also known as Heck's disease, is caused by HPV types 13, 32 and 57. It is most commonly found on the lower lip but also on the buccal mucosa, gums and tongue. It is mainly a disease of native Americans and Greenlander Eskimos. EBV causes an oral hairy leukoplakia in patients with AIDS. Pachyonychia Congenita patients commonly develop a benign oral leukoplakia, while Dykeratosis Congenita patients develop a premalignant oral leukoplakia.

Answer 326

►C Corynebacterium tenuis is the causative organism associated with most cases. Although up to 33% of adults have colonization by this bacterium in the inguinal or axillary regions, factors such as hyperhidrosis predispose to more extensive growth and resultant clinical manifestations.

Answer 327

►D Inhalation anthrax is the most lethal form of anthrax. Other forms include cutaneous anthrax and GI anthrax. The classic radiographic finding is a widened mediastinum.

Answer 328

►A Gonococcemia is characterized by sparsely distributed hemorrhagic vesiculopustules on the palms, soles, and over joints with associated fever, chills, arthralgias, and malaise. Recurrent cases associated with complement deficiencies (C5-C8). Treatment is with IV ceftriaxone.

Answer 329

►B While herpes zoster can be seen in the dermatome of any cranial or spinal nerve, the most common single nerve involved is the trigeminal nerve.

Answer 330

►A Hebra nose deformity is seen in Rhinoscleroma which is caused by Klebsiella pneumoniae subspecies rhinoscleomatis.

Answer 331

►A The clinical description and lesion shown in the image suggest a diagnosis of erysipeloid, caused by Erysipelothrix rhusiopathiae. The treatment of choice is penicillin.

Answer 332

►A Vaccinia virus is used to vaccinate high-risk individuals against smallpox virus. Development of a vesicle or ulcer with 4 cm of surrounding erythema is a reaction considered to have a high rate of adequate immunization.

Answer 333

►A When a C-section is performed in the setting of active cervical lesions of HSV, the risk of maternal- fetal transmission is decreased to 1%. If a child were delivered

Answer 334

►C Sporotrichoid spread may be seen in cutaneous leishmaniasis, actinomycosis, atypical mycobacterial infections, deep fungal infection, and melanoma. Mycobacterium marinum is associated with skin injury followed by exposure to contaminated water, usuall y from an aquarium, lake, or pool. The treatment of choice for M. marinum infections is minocycline.

Answer 335

►A This patient has rhinoscleroma, a chronic granulomatous infection of the nose and upper respiratory tract by Klebsiella pneumoniae rhinoscleromatis. The disease is endemic in Africa, Southeast Asia, Mexico, Central and South America, and Central and Eastern Europe and is rarely reported in the United States. Presentation may vary from rhinitis to diffuse airway obstruction. Mikulicz cells are foamy, vacuolated macrophages seen in rhinoscleroma. Antibacterial therapeutic choices include ciprofloxacin, tetracycline, and rifampin. Surgical treatment may be required for obstructive lesions.

Answer 336

►A Swimming pool granuloma or fish tank granuloma is caused by M. marinum and begins as a small plaque at the site of inoculation and evolves to a granulomatous plaque. It occurs as a sporotrichoid spread. The treatment is minocycline.

Answer 337

►B The body louse or Pediculus humanus corporis transmits Rickettsia prowasekii the organism responsible for epidemic typhus. Endemic typhus or murine typhus is caused by R. typhi that is transmited by the rat flea/Xenopsylla cheopis. Scrub typhus is caused by R. tsutsugamushi and is transmitted by chiggers or trombiculid mite larvae.

Answer 338

►E Whitmore disease also known as Melioidosis is characterized by pulmonary disease, septicemia, and miliary abscesses. It is caused by Burkholderia pseudomallei.

Answer 339

►D Ramsay Hunt syndrome results from varicella zoster virus infection of the geniculate ganglion of the seventh cranial nerve (CN VII). It is characterized by vesicles on the external ear or ear canal, tinnitus and/or other auditory symptoms, and ipsilateral facial paresis.

Infectious diseases of the skin Flashcards

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