common skin infections

Question 1

what is tinea capitis

Answer 1

An infection of scalp hair follicles and the surrounding skin, caused by dermatophyte fungi

Tinea capitis is a fungal infection of the scalp, involving both the skin and hair. It is also known as scalp ringworm.

Question 2

common organisms to cause tinea capitis

Answer 2

Microsporum canis

Trichophyton tonsurans.

Question 3

classification for tinea capitis

Answer 3

Ectothrix (dermatophyte infection remains confined to the hair surface) e.g. M. canis

Endothrix (dermatophyte infections of the hair that invade the hair shaft and internalize into the hair cell) e.g. T. tonsurans, most common in the UK

Favus: Honeycomb destruction of hair shaft

Question 4

tinea capitis seen commonly in who

Answer 4

Most commonly seen in healthy preadolescent children and immunocompromised adults

Question 5

clinical features of tinea capitis

Answer 5

Scale, bald patches, regional lymphadenopathy

Kerion (abscess caused by fungal infection)

Question 6

what Ix one ca do for tinea capitis

Answer 6

1) Wood’s lamp
Some dermophyte fungi e.g. ectothrixMicrosporumspecies demonstrate bright green fluorescence of infected hairs
Others don’t (e.g. nonfluorescent Trichophyton infection)

2) Dermoscopy
Black dot hairs, comma shaped hairs, cork-screw hairs

3) Specimens for microscopy + culture (diagnostic)
Scalpel scraping, hair pluck, brush or swab as appropriate to the lesion

Question 7

risk factors of tinea capitis

Answer 7

animal contact
household crowding
lower socioeconomic status
warm humid environments
contact sport.

Question 8

complications of tinea capitis

Answer 8

alopecia
scarring alopecia - bald patches
erythema nodosum
ID reaction - get after starting the antifungal treatment

Question 9

what would you see under a dermoscope for tinea capitis

Answer 9

Comma hairs

Corkscrew hairs

Zigzag hairs

Barcode-like (Morse code-like) hairs

Bent hairs.

Question 10

tinea capitis DD

Answer 10

Alopecia areata and trichotillomania; cause patchy alopecia but are not scaly

Seborrhoeic dermatitis, atopic dermatitis, and scalp psoriasis; may mimic non-inflammatory tinea capitis, but the scale is usually more diffuse

Discoid lupus erythematosus and lichen planopilaris; cause scarring alopecia

Question 11

tinea capitis management

Answer 11

4 weeks of systemic medication

Prescribe either oral griseofulvin (licensed) or oral terbinafine (off-label) empirically until culture results are available.

If the person lives in an urban area, start treatment with terbinafine for 4 weeks. - trichophyton tonsurans

If the person lives in a rural area, start treatment with griseofulvin for 4–8 weeks - griseofulvin

selenium sulfide or ketoconazole shampoo to be used at least twice weekly for 2–4 weeks, or an imidazole cream (in children less than 5 years of age) to be used daily for one week.

Question 12

what is tinea corpis

Answer 12

Trunk and limbs

Itchy circular/annular rash with a clearly defined raised and scaly edge

Usually treat with topical antifungals; oral antifungals if unsuccessful

Question 13

what is tinea cruris

Answer 13

involvement of groin and natal cleft

See management of Tinea cruris; may also benefit from topical corticosteroids for pruritus

Question 14

what is tinea pedis and how does it look

Answer 14

athlete’s foot

moist scaling and fissuring in toewebs
spreads to sole and dorsal aspect of the foot

Question 15

what is tinea manuum

Answer 15

Infection of the hand

Less common than infection of the foot

Scaling and dryness in the palmar creases

Question 16

what is tinea unguium

Answer 16

ONYCHOMYCOSIS
Infection of the nail

Yellow discolouration, thickened and crumbly nail

Can lead to nail dystrophy

Mild infections can be managed with topical antifungals, oral antifungals often required for cure

Question 17

What is tinea incognita

Answer 17

Inappropriate treatment of tinea infection with topical or systemic corticosteroids
Original infection also extends
Management: Cessation of steroid and standard antifungal treatment

Question 18

features of cellulitis

Answer 18

• Dimpled skin (peau d’orange)
• Warmth
• Blistering
• Erosionsand ulceration
• Abscessformation
• Purpura:petechiae,
  ecchymoses, or haemorrhagicbullae

Systemic features
Fever
Malaise
Lymphangitis

Question 19

what is cellulitis

Answer 19

A common bacterialinfectionthat involves the deep subcutaneous tissue

localisedarea of red, painful, swollen skin, andsystemicsymptoms

Question 20

causes of cellulitis

Answer 20

Streptococcus pyogenes, Staphylococcus aureus

Question 21

risk factors of cellulitis

Answer 21

Breaks in skin barrier: Wounds, ulcers, athlete’s foot, insect bites, IVDU, pressure sores

Poor venous flow / lymphatic drainage

Immunosuppression

Diabetes, chronic kidney disease, chronic liver disease

Obesity, pregnancy, alcoholism

Question 22

investigations for cellulitis

Answer 22

Bloods: Inflammatory markers, Anti-streptococcal O titre (ASOT)

increase in CRP, leukocytosis

Skin swab

Imaging if required

Question 23

management for cellulitis

Answer 23

Systemic antibiotics (usually oral); often penicillin-based e.g. Flucloxacillin, benzyl

Potential alternatives if penicillin-allergic: Clindamycin, Doxycycline, Vancomycin

Question 24

complications of cellulitis

Answer 24

Necrotisingfasciitis

Gasgangrene

Severesepsis

Infection of other organs, e.g. osteomyelitis, meningitis, pneumonia

Endocarditis

Question 25

what is erysipelas

Answer 25

Superficial form of cellulitis: Affects the upper dermis and extends into the superficial cutaneous lymphatics

Question 26

differentials of cellulitis

Answer 26

Eczema/dermatitis due to stasis, contact factors ``` Fungal infection eg tinea corporis, tinea pedis Drug eruption Psoriasis Lipodermatosclerosis Thrombophlebitis Insect bites and stings Radiation damage following radiotherapy Inflammatory breast cancer (carcinoma erysipeloides). ```

Question 27

how to differentiate between erysipelas and cellulitis

Answer 27

erysipelas - well defined border

Question 28

clinical features of erysipelas

Answer 28

sharp and raised border It is bright red, firm and swollen. It may be finely dimpled (like an orange skin). It may be blistered, and in severe cases may become necrotic. Bleeding into the skin may cause purpura. Cellulitis does not usually exhibit such marked swelling but shares other features with erysipelas, such as pain and increased warmth of affected skin. In infants, it often occurs in the umbilicus or diaper/napkin region. Bullous erysipelas can be due to streptococcal infection or co-infection with Staphylococcus aureus (including MRSA). abrupt in onset and often accompanied by fevers, chills and shivering. Erysipelas predominantly affects the skin of the lower limbs, but when it involves the face, it can have a characteristic butterfly distribution on the cheeks and across the bridge of the nose.

Question 29

complications of erysipelas

Answer 29

- Persistence of risk factors - Lymphatic damage (hence impaired drainage of toxins). RARE Abscess Gangrene Thrombophlebitis Chronic leg swelling Infections distant to the site of erysipelas Infective endocarditis (heart valves) Septic arthritis Bursitis Tendonitis Post-streptococcal glomerulonephritis (a kidney condition affecting children) Cavernous sinus thrombosis (dangerous blood clots that can spread to the brain) Streptococcal toxic shock syndrome (rare).

Question 30

skin manifestations of SLE

Answer 30

photosensitive 'butterfly' rash discoid lupus alopecia livedo reticularis: net-like rash

Question 31

what is pityriasis versicolor

Answer 31

superficial cutaneous fungal infection caused by Malassezia furfur

Question 32

features of pityriasis versicolour

Answer 32

- most commonly affects trunk - patches may be -hypopigmented, pink or brown (hence versicolor). May be more noticeable following a suntan - scale is common - mild pruritus

Question 33

predisposing factos of pityriasis versicolor

Answer 33

- occurs in healthy individuals - immunosuppression - malnutrition - Cushing's

Question 34

management of pityriasis versicolor

Answer 34

topical antifungal =ketoconazole fail scrapings + oral itraconazole

Question 35

when can a child return to daycare if they have impetigo

Answer 35

Patients may return to school or work when they are no longer contagious which is when all lesions have crusted over or 48h after treatment starts

Question 36

how long must child wait to return to skl if they had measles or rubella

Answer 36

4 days following the onset of the rash

Question 37

what is impetigo

Answer 37

- superficial bacterial skin infection usually caused by either Staphylcoccus aureus or Streptococcus pyogenes. primary infection or a complication of an existing skin condition such as eczema (in this case), scabies or insect bites.

Question 38

where does impetigo tend to occur

Answer 38

anywhere on the body but lesions tend to occur on the face, flexures and limbs not covered by clothing.

Question 39

how is impetigo spread

Answer 39

Spread is by direct contact with discharges from the scabs of an infected person. The bacteria invade the skin through minor abrasions and then spread to other sites by scratching. Infection is spread mainly by the hands, but indirect spread via toys, clothing, equipment and the environment may occur.§

Question 40

incubation period for impetigo

Answer 40

4-10 days

Question 41

features of impetigo

Answer 41

'golden', crusted skin lesions typically found around the mouth very contagious

Question 42

management for impetigo

Answer 42

1) hydrogen peroxide 1% cream for 'people who are not systemically unwell or at a high risk of complications' 2) topical antibiotic creams: topical fusidic acid topical mupirocin should be used if fusidic acid resistance is suspected MRSA is not susceptible to either fusidic acid or retapamulin. Topical mupirocin should, therefore, be used in this situation Extensive disease oral flucloxacillin oral erythromycin if penicillin-allergic stay off skl 48hrs after AB Mx or til all the lesions are crusted/healed

Question 43

what is erythrasma

Answer 43

asymptomatic, flat, slightly scaly, pink or brown rash usually found in the groin or axillae.

Question 44

cause of erythrasma

Answer 44

overgrowth of the diphtheroid Corynebacterium minutissimum

Question 45

examination of erythrasma

Answer 45

Wood's light reveals a coral-red fluorescence.

Question 46

management of erythrasma

Answer 46

Topical miconazole or antibacterial are usually effective. Oral erythromycin may be used for more extensive infection

Question 47

causes of erythema nodosum

Answer 47

NO – idiopathic D – drugs (penicillin sulphonamides) O – oral contraceptive/pregnancy S – sarcoidosis/TB U – ulcerative colitis/Crohn's disease/Behçet's disease M – microbiology (streptococcus, mycoplasma, EBV and more)

Question 48

pathogen responsible for molluscum contagiosum

Answer 48

poxvirus

Question 49

management for tinea pedis

Answer 49

Management includes general measures (drying of feet, avoiding occlusive footwear etc), topical antifungals - imidazole, undecenoate - 4 weeks oral terbinafine and oral antifungals if unsuccessful

Question 50

Ix for pityriasis versicolor

Answer 50

Woods light yellow green fluorescence

Question 51

features of iron deficinecy anaemia

Answer 51

Pallor | Other signs: koilonychia, atrophic glossitis, post-cricoid webs, angular stomatitis

Question 52

polycythaemia features

Answer 52

Pruritus particularly after warm bath 'Ruddy complexion' Gout Peptic ulcer disease

Question 53

CKD features

Answer 53

Lethargy & pallor Oedema & weight gain Hypertension

Question 54

lymphoma features

Answer 54

Night sweats Lymphadenopathy Splenomegaly, hepatomegaly Fatigue

Question 55

liver disease features

Answer 55

History of alcohol excess Stigmata of chronic liver disease: spider naevi, bruising, palmar erythema, gynaecomastia etc Evidence of decompensation: ascites, jaundice, encephalopathy

Question 56

tests for suspecting impetigo

Answer 56

swabs for microbiology

Question 57

risk of prolonged use of ABx in impetigo which bacterial toxin is implicted in impetigo

Answer 57

staph aureus has shown to develop AB resistance particularly to fusidic acid if it is used for linger than 2 wekks staph aureus Group A strep

Question 58

if impetigo treatment fail intially

Answer 58

check swab and see if it sensitive to given AB

Question 59

why may there be recurrent cases of impetigo in family

Answer 59

nasal carriage of staph aureus is quite common - not eradicated by oral or topical treatment eraducated by use of antibacterial nasak ointment and antiseptic skin washes

Question 60

what is erythrasma

Answer 60

generally asymptomatic, flat, slightly scaly, pink or brown rash usually found in the groin or axillae. It is caused by an overgrowth of the diphtheroid Corynebacterium minutissimum

Question 61

examination of erythrasma

Answer 61

woods light coral red fluorescence

Question 62

Mx for erythrasma

Answer 62

Topical miconazole or antibacterial are usually effective. Oral erythromycin may be used for more extensive infection

Question 63

description of staphylococcal scalded skin syndrome

Answer 63

● Commonly seen in infancy and early childhood

Question 64

causes of staphylocco

Answer 64

● Production of a circulating epidermolytic toxin from phage group II, benzylpenicillin-resistant (coagulase positive) staphylococci

Question 65

RFs of erysipelas

Answer 65

- previous episode - breaks in the skin barrier current/prior injury - exposure of umbilical cord and vaccination injury - nasopharyngeal infection - venous disease - immune deficiency --- diabetes --- alcoholism --- obesity --- HIV - nephrotic syndrome - pregnancy

Question 66

causes of erysipelas

Answer 66

Strep pyogenes - group A beta haemolytic streptococci staph aureus MRSA

Question 67

Mx of erysipelas

Answer 67

- cold packs and analgesics to relieve local discomfort - elevation of an infected limb - compression stockings - wound care ABx - oral/IV pencillin

Question 68

Mx of recurrent cellulitis

Answer 68

- Avoid trauma, wear long sleeves and pants in high-risk activities, such as gardening - Keep skin clean and well moisturised, with nails well tended - Avoid having blood tests taken from the affected limb - Treat fungal infections of hands and feet early - Keep swollen limbs elevated during rest periods to aid lymphatic circulation. Those with chronic lymphoedema may benefit from compression garments.

Question 69

what is scabies

Answer 69

caused by mite sarcoptes scabiei - spread by prolonged skin contact

Question 70

pathophysiology of scabies

Answer 70

mite burrows into the skin, laying its eggs in the stratum corneum intense pruritis ass w scabies is due to a delayed type IV hypersensitivity reaction to mites/eggs which occurs about 30 days after the initial infection

Question 71

features of scabies

Answer 71

- widespread pruritus - linear burrows on the side of fingers, interdigital webs and flexor aspects of the wrist - in infants the face, scalp may also be affected - 2 Features - scratching: excoriation, infection

Question 72

Mx of scabies and what do u tell the family

Answer 72

FIRST LINE - premethrin 5% SECOND LINE - malathion 0.5% - pruritus persists up to 4- 6 weeks post eradication - avoid close physical contact with others until treatment is complete - all household and close physical contacts should be treated at the same time, even if asymptomatic - kill off mites with high heat

Question 73

what is crusted scabies (Norwegian) Mx

Answer 73

crusted scabies in pts with suppressed immunity esp HIV Ivermectin

Question 74

causes of onychomycosis

Answer 74

- dermatophytes - - Trichophyton rubrum yeasts - candida - non-dermatophyte moulds

Question 75

RFs for fungal nail infections

Answer 75

diabetes mellitus | increasing age

Question 76

DD for onychomycosis

Answer 76

psoriasis repeated trauma lichen planus yellow nail syndrome

Question 77

Ix of onychomycosis

Answer 77

nail clippings | scrapings of the affected nail

Question 78

Mx of onychomycosis

Answer 78

Diagnosis should be confirmed before starting treatment Dermatophyte - oral terbinafine FIRST LINE 6 weeks to 3 months therapy Candida - topical antifungals really severe ORAL ITRACONAZOLE period of 12 weeks topical Tx upto 6 months for fingernails and 9-12 months for toenails

Question 79

what is hidradenitis suppurativa characterisitcs suspected in who

Answer 79

chronic, painful, inflammatory skin disorder. characterised by the development of inflammatory nodules, pustules, sinus tracts and scars in intertriginous areas. suspected in pubertal or post-pubertal patients who have a diagnosis of recurrent furnucles or boild

Question 80

epidemiology and pathogenesis of hidradenitis suppurativa

Answer 80

epi - women are more likely to devleop HS than men - under 40 path - chronic inflam occlusion of folliculopilosebaceous units that obstructs the apocrine glands and prevents keratinocytes from propely shedding from the follicular epithelium

Question 81

RFs of hidradenitis suppurativa

Answer 81

FH smoking obesity, diabetes, PCOS mechanical stretching of skin

Question 82

clinical features of hidradenitis suppurativa

Answer 82

- > Initial manifestation involves recurrent, painful, and inflamed nodules. - > HS occurs most commonly on intertriginous skin. However, non-intertriginous skin involvement also can occur. The axilla is the most common site - > Other areas include inguinal, inner thighs, perineal and perianal, inframammary skin. - > The nodules may rupture, discharging purulent, malodorous material. - > Coalescence of nodules can result in plaques, sinus tracts and 'rope-like’ scarring.

Question 83

Mx of hidradenitis supparativa

Answer 83

- Encourage good hygiene and loose-fitting clothing - Smoking cessation - Weight loss in obese - Acute flares can be treated with steroids (intra-lesional or oral) or flucloxacillin. Surgical incision and drainage may be needed in some cases. - Long-term disease can be treated with topical (clindamycin) or oral (lymecycline or clindamycin and rifampicin) antibiotics. - Lumps that persist despite prolonged medical treatment are excised surgically.

Question 84

complications of hidradenitis supparativa

Answer 84

- Sinus tracts, fistulas - Comedones - Scarring - severe scarring can lead to dense, rope-like bands in the skin with strictures and lymphedema - Contractures - Lymphatic obstruction

Question 85

DDx of hidradenitis supparativa

Answer 85

- Acne vulgaris - It primarily occurs on the face, upper chest, and back, whereas HS primarily involves intertriginous areas. - Follicular pyodermas (folliculitis, furuncles, carbuncles) - Unlike HS, follicular pyodermas are transient and respond rapidly to antibiotics - Granuloma inguinale (donovanosis) - It is a sexually transmitted infection caused by Klebsiella granulomatis. Suspect donovanosis if there is an enlarging ulcer that bleeds in the inguinal area.

Question 86

features of seborrhoeic dermatitis ass

Answer 86

nflammatory reaction related to a proliferation of a normal skin inhabitant, a fungus called Malassezia furfur eczematous lesions on the sebum-rich areas: scalp (may cause dandruff), periorbital, auricular and nasolabial folds otitis externa and blepharitis may develop HIV parkinson scalp - T-gel - zinc pyrithione ketoconazole selenium sulphide and topical corticosteroid may also be useful Face and body management topical antifungals: e.g. ketoconazole topical steroids: best used for short periods difficult to treat - recurrences are common

Question 87

mosaic warts

Answer 87

It is a cluster of viral warts sometimes several cm in diameter Topical salicyclic preparations after soaking and rubbing away hard skin (may work better if covered by tape overnight). Treatment takes a long time and perseverance is essential. Repeated liquid nitrogen application may be required and will be difficult on an extensive area. Formalin soaks several times per week can be used. Other specialist treatment can include bleomycin intralesional injections. It is reasonable to do nothing as most warts eventually disappear spontaneously