Skin infections and infestations

Question 1

Causes of Bacterial skin infections

Answer 1

Staphs Aureus and strep pyogenes 
impetigo both
folliculitis - pseudomonas from dirty hot tubs
erysipelas - strep
cellulitis - staph

Question 2

Causes of Viral skin infections

Answer 2

HPV, molluscum contagiosum (MCV), HSV, VZV,

Question 3

Causes of Fungal skin infections

Answer 3

Tinea (ringworm) and Candida

Question 4

Skin infestations

Answer 4

Lice or scabies (or the more severe crusted/norwegian form in immunosuppressed)

Question 5

Tropical skin infections

Answer 5

Leishmaniasis or leprosy

Question 6

Factors which predispose to cutaneous infections

Answer 6

Pre-existing skin disease –> eczema, bacterial/viral infection
Immunosuppression –> HIV or transplant. Chronic disease –> diabetes (particularly for bacterial/fungal). Social circumstances –> scabies and lice. Travel –> Leishmaniasis or leprosy

Question 7

Impetigo

Answer 7

cutaneous bacterial infection of stratum corneum - symptoms from tissue invasion and toxins. Mainly children/contact sports and highly contagious - 10-20% of normal pop carry impetigo. If blistering bullous impetigo –> treat with topical fusidic acid if small or oral Flucloxacillin. Ecthyma is ulcerating impetigo. If widespread and systemically unwell likely not impetigo.

Question 8

Staphylococcus scalded skin syndrome (SSSS)

Answer 8

Erythematous skin with sheets of desquamation
Fever and irritability – mainly children
Will usually resolve 7-14 days – treat with flucloxacillin
Caused by exotoxin included in a phage (71)

Question 9

Erysipelas

Answer 9

A well demarcated, raised dermal infection caused by strep group A
(Pyogenes) Also called st antony’s fire
Most common on face and lower limbs - presents with 48hrs of general illness

Question 10

Cellulitis

Answer 10

Bacterial infections of the skin spreading to the subcut fat
Most common on face and lower limbs
Can be staph or strep.

Question 11

Treatment of Bacterial skin infections

Answer 11

1g Amoxycillin TDS or Penicillin V 1g daily for 2 weeks

If recurrent need long term antibiotics. 2nd line for cellulitis is flucloxaxillin. D

Question 12

Folliculitis

Answer 12

Inflammation in hair follicles usually due to staph aureus – can occlude the follicules leading to pustules. Management –> aseptic washes, topical antibiotics or oral fluclokacillin

Question 13

Carbuncles

Answer 13

infection in both follicle and subcutaneous tissue

Question 14

Human papilloma virus (HPV)

Answer 14

Skin and genitals worse effected – major carcinogenic effect
Produces warts – treat with cryotherapy, salicytic acid or CO2 laser curettage

Question 15

Herpes simplex virus (HSV)

Answer 15

Type 1 classically oral(painful oral ulceration), type 2 genital - spread by contact ‘shedding’
Latent in sensory root ganglion between eruptions - brought on by cold, trauma, sun or immunosuppression (stress)
Treat with aciclovir

Question 16

Varicella Zoster virus (VZV)

Answer 16

Chickenpox - 14 day incubation, 2-4 days of skin rash - infections two days before and 5 after rash onset
Shingles - reactivation with pain before vesicles in dermatomal distribution - treat aciclovir (prednisolone)

Question 17

Molluscum contagiosum

Answer 17

A highly infectious pox virus - 7% incidence in children
Resolves spontaneously over months–> years
Larger lesions in HIV. H202 or cryotherapy can be used to speed resolution. small wart-like lesions

Question 18

Candida skin infections

Answer 18

Hyphae forming yeast commensal - creamy white patches on mucus membranes, angular chelitis
Mainly problem in immunosuppressed (HIV or babies)
Treat iwth fluconazole or nystatin

Question 19

Tinea - Corporis/capitis/pedis (Ringworm)

Answer 19

Annular, demarcated lesions with a palpable edge
Can have scaling, pustules or vesicles
Treat with terbinafine or ketoconazole

Question 20

Scabies

Answer 20

Burrowing mites which cause intensely itchy papules – barrows in skin folds at hands and groin
All contacts need treatment
2x insecticide one week apart
Itching may last for 4-6wks post eradication

Question 21

Lice

Answer 21

head or pubic hair – only need to treat if live lice seen,
2x insecticide one week apart.
Treat with wet combing, malathion, dimeticone, isopropyl myristate and cyclomethicone

Question 22

Leishmaniasis

Answer 22

Can effect skin, mucus membranes or organs
2million cases/yr in 88 countries
Sandfly vector bites –> nodule –> ulcer
Treat with pentovalent antimonials (Na stibogluconate)

Question 23

Leprosy

Answer 23

Can be tuberculoid or lepromatous disease depending on immunological status
Mechanism of transmission unknown
Treat with Dapsone, rifampicin, clofazimine

Question 24

Molluscum Contagiosum

Answer 24

A highly infectious skin infection caused by a DNA pox virus which typically causes small, pearly, umbilicated lesions in young children. Cryotherapy, topical agents and surgery may be effective in removing the lesions. transmission is by skin contact and outbreaks in schools are common.

Question 25

Progression of Molluscum contagiosum

Answer 25

Incubation is usually 2-7wks but can be up to 6months. Lesions may be present up to 12months and usually self-limit within 18months.

Question 26

Fungal Nail infections (Onychomycosis)

Answer 26

90% dermatophyes - trichophyton rubrum. But also candida or non-dermatophyte moulds. Unsightly, thickened, rough, opaque nails are commonest finding. Confirm diagnosis by micro then with oral terbinafine or itraconazole (3months for finger nails, 3-6months for toenails).

Question 27

Systemic causes of Pruritus

Answer 27

Liver disease - Hx of alcohol abuse and signs of liver failure
Iron deficiency Anaemia - pallor, atrophic glossitis, angular stomatitis
Polycythaemia - Itching after warm bath, Ruddy complexion, Gout, peptic ulceration
Kidney disease – Lethargy & pallor, oedema and weight gain, HTN
Lymphoma – night sweats, splenomegaly, hepatomegaly, fatigue

Question 28

Athletes Foot

Answer 28

Tinea pedis - caused by trichophyton fungus. Causes scaling, flaking and itching between the toes. treat topical imidazole, undecenoate or terbinafine.

Question 29

Painful blistering rash

Answer 29

Probably shingles - not many things which cause pain and blistering.

Question 30

Erythrasma

Answer 30

An asymptomatic, flat, slightly scaled pink to brown rash found in the groin or axillae. Due to overgrowth of corynebacterium minutissimum. Coral-red fluorescence under Wood’s light. Topical miconazole or antibacterials or oral erythromycin if more extensive.