Dermatology infections

Question 1

Impetigo

Answer 1

Superficial bacterial skin infection usually caused by either staph aureus or strep pyogenes

Can be a primary infection or a complication of an existing skin condition

Question 2

Impetigo pathophysiology

Answer 2

Direct contact with discharges from the scabs of an infected person

Spread mainly by the hands, but indirect spread via toys, clothing, equipment & environment may occur

Incubation period is between 4-10 days

Question 3

Impetigo clinical features

Answer 3

Lesions tend to occur on the face, flexures & limbs not covered by clothing

‘Golden’ crusted skin lesions typically found around the mouth

Very contagious

Question 4

Impetigo mx

Answer 4

Limited, localised disease - hydrogen peroxide 1% cream for those ‘systemically unwell or high risk of complications’

• can give topical antibiotic creams eg. fusidic acid/mupirocin

Extensive disease - PO flucloxacillin/erythromycin

School exclusion - excluded from school until lesions are crusted & healed OR 48 hours after commencing abx treatment

Question 5

Folliculitis

Answer 5

Inflammation of a hair follicle that results in the formation of papules or pustules

Question 6

Folliculitis aetiology

Answer 6

Predominantly bacterial infections - staph aureus

Eosinophilic folliculitis - sterile & most commonly arises in the context of immunosuppression (HIV)

Question 7

Folliculitis clinical features

Answer 7

Presence of papules and pustules

Can appear anywhere on the body except palms of hands & soles of feet

Question 8

Folliculitis mx

Answer 8

Topical abx with suggested addition of antibacterial soaps

Oral abx in severe cases

Question 9

Chicken pox

Answer 9

Caused by primary infection with varicella zoster virus

Question 10

Chicken pox clinical features

Answer 10

Fever initially

Itchy, rash starting on head/trunk before spreading

Initially macular then papular then vesicular

Systemic upset usually mild

Question 11

Chicken pox mx

Answer 11

Supportive - cool, trim nails, calamine lotion

School exclusion - most infectious period is 1-2 days before rash appears but infectivity continues until all lesions are dry and have crusted over (usually 5 days after)

Immunocompromised patients/newborns - VZIG (if chickenpox develops → IV aciclovir should be considered)

Question 12

Chicken pox complications

Answer 12

Secondary bacterial infection of the lesions

Pneumonia

Encephalitis

Disseminated haemorrhagic chickenpox

Arthritis, nephritis & pancreatitis → very rarely seen

Question 13

Shingles

Answer 13

Acute, unilateral, painful blistering rash caused by reactivation of the VZV

Question 14

Shingles triggers

Answer 14

Emotional stress

Immunosuppression - chemo, high dose steroids

Recent illness or surgery

Skin injury - sunburn, trauma

Question 15

Shingles clinical features

Answer 15

Prodrome - acute neuralgia, non-specific symptoms, enlarged lymph nodes, 2-3 days long

Infectious phase - rash (unilateral, affecting a single dermatome, initially erythematous & macular → erythematous papules → vesicles/bullae), pain, 7-10 days

Resolution phase - vesicular rash crusts over within 10-12 days of rash onset

Question 16

Shingles mx

Answer 16

Remind patients they are potentially infectious - avoid immunosuppressed, until veiscles are crusted over
Analgesia - paracetamol & NSAIDs; oral corticosteroids if pain is severe & not responding to above
Antivirals - within 72 hours for the majority of patients -> reduced incidence of post-herpetic neuralgia
- aciclovir, famciclovir or valaciclovir

Question 17

Shingles complications

Answer 17

Post-herpetic neuralgia

Herpes zoster ophthalmicus - occurs where shingles involves ophthalmic branch of CN V

Ramsey-Hunt syndrome - CN VII affected

Encephalitis

Question 18

Shingles prevention

Answer 18

Shingles vaccine

• offered to all patients aged 70-79 years
• live-attenuated & given subcutaneously
• SEs - chickenpox, injection site reactions

Question 19

Viral warts

Answer 19

Cutaneous warts are small, rough growths that are caused by infection of keratinocytes with HPV

Can appear anywhere but are commonly seen on the hands & feet

Usually spread by direct skin-to-skin contact or indirectly via contact with contaminated floors or surfaces

Question 20

Viral warts mx

Answer 20

Most resolve without treatment

Advice offered on reducing the risk of transmission & limiting personal spread of warts

Treatment considered if wart is painful, unsightly, persistent or requested:

• topical salicylic acid
• cryotherapy
• combination of both

Referral to dermatologist if complex

Question 21

Molluscum contagiosum

Answer 21

Common skin infection caused by MCV, a member of the Poxviridae family

Majority of cases occur in children, with maximum incidence in preschool children aged 1-4 years

Question 22

Molluscum contagiosum clinical features

Answer 22

Characteristic pinkish or pearly white papules with a central umbilication

Lesions appear in clusters in areas anywhere on the body (except the palms of the hands & soles of the feet)

Commonly seen on the trunk & in flexures

Question 23

Molluscum contagiosum mx

Answer 23

Self-care advice - reassure people that molluscum contagiosum is self-limiting, lesions are contagious, exclusion not necessary

Treatment not usually recommended - simple trauma or cryotherapy can be considered

Question 24

Tinea

Answer 24

Superficial fungal infection of the skin caused by dermatophytes, a group of fungi that invade and grow in dead keratin

Commonly known as ringworm

Question 25

Tinea clinical features

Answer 25

Red, scaly patch that often has an area of central clearing, giving it a ring-like appearance

Affected area may be itchy

Question 26

Tinea ix

Answer 26

Culture of skin scrapings

Question 27

Tinea mx

Answer 27

Topical antifungals - clotrimazole & ketoconazole

Tinea capitis & onychomycosis → systemic agents eg. terbinafine/itraconazole are recommended

Question 28

Candidiasis

Answer 28

Caused by Candida albicans that is normally present in the mouth

Question 29

Oral candidiasis clinical features

Answer 29

White or creamy patches on the tongue, inner cheeks, gums, tonsils or roof of the mouth

Pain

Discomfort whilst eating or drinking

Can spread to oesophagus → dysphagia

Question 30

Candidiasis mx

Answer 30

Risk factor modification - optimise glycaemic control, proper denture hygiene, rinse mouth after using ICS

Antifungal therapy - nystatin suspension or miconazole gel

Severe or refractory cases - oral fluconazole

Question 31

Scabies clinical features

Answer 31

Widespread pruritus

Linear burrows on the side of fingers, interdigital webs & flexor aspects of the wrist

In infants → face & scalp may also be affected

Secondary features are seen due to scratching

Question 32

Scabies mx

Answer 32

Permethrin 5% first line

Pruritus persists for up to 4-6 weeks post eradication

Avoid close physical contact with others until treatment complete

All household & close physical contacts should be treated at same time

Launder, iron or tumble dry clothing, bedding, towels → kill off mites

Question 33

Lice

Answer 33

Parasitic insects that infest the hairs of the human head & feed on blood from the scalp

Question 34

Lice diagnosis

Answer 34

Detection combing → best way to confirm the presence of lice

• systematic combing of wet/dry hair using a fine-toothed head lice detection comb

Diagnosis only made if a live head louse is found

Question 34

Lice mx

Answer 34

Should only be treated if a live head louse is found

All affected household members should also be treated on the same day

Can be treated with one of the following:

• physical insecticide eg. dimeticone 4% lotion
• traditional insecticide eg. malathion 0.5% aqueous liquid

Children who are being treated for head lice can still attend school