infestations and infections of the skin Flashcards

Question

what is necrotising faciitis?

Answer 1

Initial dusky induration (usually of a limb), followed by rapid painful necrosis of skin, connective tissue and muscle. Potentially fatal Usually synergistic: streptococci, staphylococci, enterobacteriaceae and anaerobes. Prompt diagnosis essential (requires high index of suspicion), followed by broad-spectrum parenteral antibiotics and surgical debridement. MRI can aid diagnosis. Blood and tissue cultures can determine organisms and sensitivities. Mortality is high. Can affect the scrotum (Fournier’s gangrene).

Answer 2

Important cause of infection in immunosuppressed states. Mycobacterium marinum causes indolent granulomatous ulcers (fish-tank granuloma) in healthy people - Sporotrichoid spread (spread olong the lymphatics) Mycobacterium chelonae & abscessus - puncture wounds, tattoos, skin trauma or surgery Mycobacterium ulcerans: an important cause of limb ulceration in Africa (Buruli ulcer) or Australia (Searle’s ulcer).

Answer 3

Annular erythema develops at site of the bite of a Borrelia-infected tick Bite form Ixodes tick infected with Borrelia burgdorferi Initial cutaneous manifestation: Erythema migrans (only in 75%) - Erythematous papule at the bite site - Progression to annular erythema of >20cm 1-30 days after infection, fever, headache Multiple secondary lesions develop - similar but smaller to initial lesion Neuroborreliosis: - Facial palsy / other CN palsies - Aseptic meningitis - Polyradiculitis Arthritis – painful and swollen large joints (knee is the most affected join) Carditis Serology not sensitive Histopathology - non-specific High index of suspicion required for diagnosis

Answer 4

Caused by Francisella tularensis Acquired through: - Handling infected animals (squirrels and rabbits) - Tick bites - Deerfly bites Ulceroglandular form Primary skin lesion is small papules at inoculation site that rapidly necroses – leading to painful ulceration +/- local cellulitis Painful regional lymphadenopathy Systemic symptoms: fever, chills, headache and malaise

Answer 5

Pseudomonas aeruginosa Usually occurs in neutropaenic patients Red macule(s) → oedematous → haemorrhagic bullae. May ulcerate in late stages or form an eschar surrounded by erythema

Answer 6

``` Pseudomonas Aspergillosis Leishmaniasis Cryptococcosis Lues maligna Rickettsial infections Cutaneous anthrax Tularaemia Necrotic arachnidism (brown recluse spider bite) Scrub typhus (Orientia tsutsugamushi) Rat bite fever (Spirillum minus) Staphylococcal or streptococcal Ecthyma Lyme disease. ``` Compare normal human anatomy & pathology and physiology and pathophysiology of key diseases, disorders and clinical presentations throughout the human life cycle

Answer 7

caused by Treponema pallidum (bacteria) Primary infection: Chancre -painless ulcer with a firm indurated border Painless regional lymphadenopathy one week after the primary chancre Chancre appears within 10-90 days

Answer 8

Begins ~50 days after chancre Malaise, fever, headache, pruritus, loss of appetite, iritis ‘Great mimicker’ – low threshold for testing - Rash (88-100%) -Pityriasis rosea-like rash - Alopecia (‘moth-eaten’) - Mucous patches - Lymphadenopathy - Residual primary chancre - Condylomata lata - Hepatosplenomegaly

Answer 9

Rare manifestation of secondary syphilis Pleomorphic skin lesions with pustules, nodules and ulcers with necrotising vasculitis More frequent in HIV manifestation

Answer 10

Gumma Skin lesions - nodules and plaques Extend peripherally while central areas heal with scarring and atrophy Mucosal lesions extend to and destroy the nasal cartilage Cardiovascular disease Neurosyphilis (general paresis or tabes dorsalis)

Answer 11

diagnosis: Clinical findings Serology Strong index of suspicion required in 2ndary syphilis Treatment: IM benzylpenicillin or oral tetracycline

Answer 12

Mycobacterium leprae Obligate intracellular bacteria - predominantly affects skin & nerves, but can affect any organ Clinical spectrum: - Lepromatous leprosy - Multiple lesions: macules, papules, nodules - Sensation and sweating normal (early on) - Tuberculoid leprosy - Solitary or few: elevated borders – atrophic center, sometimes annular - Hairless, anhidrotic, numb

Answer 13

Can affect any organ system, including the skin Only 5-10% of infections lead to clinical disease Cutaneous TB may be acquired: - Exogenously (primary-inoculation TB and tuberculosis verrucosa cutis) - Contiguous endogenous spread – (scrofuloderma )or autoinoculation – periorificial tuberculosis - Haematogenous/lymphatic endogenous spread –dissemination (lupus vulgaris, miliary tuberculosis, gummas Investigations: - Interferon-γ release assay (Quantiferon-TB) - Histology – ZN stain - Culture / PCR

Answer 14

Tuberculous chancre - painless, firm, reddish-brown papulonodule that forms an ulcer Tuberculosis verrucosa cutis - wart-like papule that evolves to form redbrown plaque Scrofuloderma – subcutaneous nodule with necrotic material - becomes fluctuant and drains, with ulceration and sinus tract formation. Orificial TB - non-healing ulcer of the nasal mucosa that is painful Lupus vulgaris – red brown plaque - +/- central scarring, ulceration Miliary TB - pinhead-sized, bluish-red papules capped by minute vesicles Tuberculous gumma – firm subcutaneous nodule - later ulcerates

Answer 15

Poxvirus infection Common in children & immunocompromised Differential diagnosis - Verrucae - Condyloma acuminata - Basal cell carcinoma - Pyogenic granuloma Usually resolve spontaneously Treatment options – curettage (scraped off), imiquimod, cidofovir

Answer 16

Primary and recurrent vesicular eruptions Favour orolabial and genital regions Transmission can occur even during asymptomatic periods of viral shedding HSV-1 – direct contact with contaminated saliva / other infected secretions HSV-2 - sexual contact Replicates at mucocutaneous site of infection -> Travels by retrograde axonal flow to dorsal root ganglia

Answer 17

Symptoms with 3-7 days of exposure Preceded by tender lymphadenopathy, malaise, anorexia ± Burning, tingling Painful rouped vesicles on erythematous base → ulceration / pustules / erosions with scalloped border Crusting and resolution within 2-6 weeks Orolabial lesions – often asymptomatic Genital involvement – often excruciatingly painful→ urinary retention Systemic manifestations– aseptic meningitis in up to 10% of women Reactivation – spontaneous, UV, fever, local tissue damage, stress

Answer 18

emergency occurs in people with atopic eczema Monomorphic, punched out erosions (excoriated vesicles) happens in babies treated with IV acyclovir and accompanying antibiotics

Answer 19

HSV (1>2) infection of digits – pain, swelling and vesicles (vesicles may appear later) Misdiagnosed as paronychia or dactylitis Often in children

Answer 20

HSV 1 involvement of cutaneous site reflecting sites of contact with another athlete’s lesions Contact sports e.g. wrestling

Answer 21

Exposure to HSV during vaginal delivery – risk higher when HSV acquired near time of delivery HSV 1 or 2 Onset from birth to 2 weeks Localised usually – scalp or trunk Vesicles → bullae erosions Encephalitis → mortality >50% without treatment, 15% with treatment → neurological deficits Requires IV antivirals

Answer 22

Immunocompromised patients e.g. HIV / transplant recipient Most common presentation – chronic, enlarging ulceration Multiple sites or disseminated Often atypical e.g. verrucous, exophytic or pustular lesions Involvement of respiratory or GI tracts may occur

Answer 23

diagnosis: Swab for Polymerase chain reaction Treatment: Don’t delay Oral valacyclovir or acyclovir 200mg five times daily in immunocompetent localised infection Intravenous 10mg/kg TDS X 7-19 days

Answer 24

Dermatomal Single dermatome Multidermatomal

Answer 25

Coxsackie A16, Echo 71 An acute self-limiting coxsackievirus infection - Echo 71 (associated with a higher incidence of neurological involvement included fatal cases of encephalitis) Prodrome of fever, malaise, and sore throat Red macules, vesicles (typically gray and eliiptical), and ulcers develop on buccal mucosa, tongue, palate and pharynx, and may also develop on hands and feet (acral and volar surfaces). Spread by direct contact via oral-oral route or oral faecal route.

Answer 26

Measles, Rubella, EBV, CMV, HHV6 & HHV7 cause morbilliform (measles-like) eruptions Leptospirosis Rickettsia (morbilliform rahes)

Answer 27

Coagulation abnormalities - TTP, ITP, DIC Vasculitis Infections Viruses - Hepatitis B, CMV, Rubella, Yellow fever, Dengue fever, West nile virus Bacterial (BREN) - Borrelia, Rickettsia, Neisseria, Endocarditis Other infections - Plasmodium falciparum, Trichinella Other - TEN, Ergot poisoning, Raynauds

Answer 28

Gianotti-Crosti syndrome aka papular acrodermatitis of childhood A viral eruption that causes and acute symmetrical erythematous papular eruption on face, extremities and buttocks – usually in children aged 1-3 years Causes: - EBV (most common) - CMV - HHV6 - Coxsackie viruses A16, B4 and B5 - Hepatitis B

Answer 29

aka 5th disezse Parvovirus B19 Initially: mild fever and headache A few days later – ‘slapped cheeks’ for 2-4 days Then reticulated (lacy) rash of chest and thighs in 2nd stage of disease

Answer 30

aka exanthem subitum aka 6th disease Children 2-5 days of high fever Followed by appearance of small pale pink papules on the trunk and head Lasts hours to 2 days. Caused by HHV6 and HHV7 (less commonly)

Answer 31

Caused by parapoxvirus Direct exposure to sheep or goats Dome-shaped, firm bullae that develop an umbilicated crust. Usually develop on hands and forearms They generally resolve without therapy in 4-6 weeks

Answer 32

caused by human papilloma viruses >200 subtypes of HPV

Answer 33

superficial eg. candida, malassezia, dermatophytes deep/soft tissue eg. chromomycosis, madura foot disseminated eg. candida, aspergillus, fusarium, histoplasma

Answer 34

Superficial Fungal Infection Hypopigmented, hyperpigmented or erythematous macular eruption +/- fine scale Malassezia spp. Begins during adolescence (when sebaceous glands become active) Flares when temperatures and humidity are high – Immunosuppression Topical azole

Answer 35

superficial fungal infections Dermatophytes – fungi that live on keratin Trichophyton rubrum causes the most fungal infections Trichophyton tonsurans causes the most tinea capitis Kerion – an inflammatory fungal infection that may mimic a bacterial folliculitis or an abscess of the scalp; scalp is tender and patient usually has posterior cervical lymphadenopathy - Frequently secondarily infected with Staphylococcus aureus

Answer 36

Trichophyton rubrum – scaling and hyperkeratosis of plantar surface of food Trichophyton mentagrophytes (interdigitale) –sometimes vesiculobullous reaction on arch or side of foot (athletes foot)

Answer 37

Aka Dermatophytid reactions Inflammatory reactions at sites distant from the associated dermatophyte infection May include urticaria, hand dermatitis, or erythema nodosum Likely secondary to a strong host immunologic response against fungal antigens

Answer 38

Follicular abscess produced when dermatophyte infection penetrates the follicular wall into surrounding dermis; tender Trichophyton rubrum or mentagrophytes are usually culprit

Answer 39

Candida albicans Predisposed by occlusion, moisture, warm temperature, diabetes mellitus Most sites show erythema oedema, thin purulent discharge Usually an intertriginous infection (affecting the axillae, submammary folds, crurae and digital clefts) or of oral mucosa. A common cause of vulvovaginitis May affect mucosae. Can become systemic (immunocompromise)

Answer 40

Capacity for deep invasion of skin or production of skin lesions secondary to systemic visceral infection. Subcutaneous fungal infections – infections of implantation (inoculation) Sporotrichosis Phaeohypomycosis Chromomycosis Mycetoma (Madura foot) Lobomycosis Rhinosporidiosis

Answer 41

Systemic respiratory endemic fungal infections Include blastomycosis, histoplasmosis, coccidiodomycosis, paracoccidoiodomycosis, penicillinosis Disease in both immunocompetent and immunosuppressed

Answer 42

eg aspergillosis

Answer 43

Risk factors: neutropaenia & corticosteroid therapy Primarily a respiratory pathogen Cutaneous lesions being as well-circumscribed papule with necrotic base and surrounding erythematous halo, Propensity to invade blood vessels causing thrombosis and infarction Lesions destructive – may extend into cartilage, bone and fascial planes Should be considered in differential of necrotisiing lesions Fusarium causes similar illness and cutaneous lesions both clinically and histologically – (septate hype with acute angle branching)

Answer 44

Presentation: fever, headache, facial oedema, proptosis, facial pain, orbital cellulitis ± cranial nerve dysfunction Apophysomyces, Mucor, Rhizopus, Absidia, Rhizomucor ``` Associations: Diabetes mellitus (1/3 of patients - DKA very high risk Malnutrition Uraemia Neutropaenia Medications: Steroids / antibiotics / desferoxamine Burns HIV ``` Treatment: aggressive debridement & antifungal therapy Culture positive in only 30% of cases

Answer 45

Contagious infestation caused by Sarcoptes species Female mates, burrows into upper epidermis, lays her eggs and dies after one month. Insidious onset of red to flesh-coloured pruritic papules Affects interdigital areas of digits, volar wrists, axillary areas, genitalia A diagnostic burrow consisting of fine white scale is often seen Crusted or ‘Norwegian’ scabies - hyperkeratosis - Often asymptomatic; found in immunocompromised individuals Treatment: permethrin, oral ivermectin - Two cycles of treatment are required

Answer 46

Pediculus humanus capitis - Entire live cycle spent in hair - 2ndary infection common - Treatment: malathion, permethrin, or oral ivermectin

Answer 47

Pediculus humanus corporis - Lives and reproduces in clothing – leaves to feed; rarely found on skin - Pruritic papules & hyperpigmentation - Found in overcrowding, poverty & poor hygiene - Eliminated by thorough cleaning or discarding clothes

Answer 48

Phithrus pubis aka crabs; three pairs of legs - Eggs found on hair shaft, also found in occipital scalp, body hair, eyebrow and eyelash, axillary hair - Treatment: malathion / permethrin, oral ivermectin

Answer 49

Cimex lectularius – reddish-brown, wingless insect resembling size and shape of ladybird - Itchy weals around a central punctum Dine alone at night, rapidly and painlessly Live behind wallpaper, under furniture Fumigation of home is necessary to get rid of pest Treatment of patient is symptomatic

infestations and infections of the skin Flashcards

(73 cards)