Skin infections and infestations Flashcards
Causes of Bacterial skin infections
Staphs Aureus and strep pyogenes impetigo both folliculitis - pseudomonas from dirty hot tubs erysipelas - strep cellulitis - staph
Causes of Viral skin infections
HPV, molluscum contagiosum (MCV), HSV, VZV,
Causes of Fungal skin infections
Tinea (ringworm) and Candida
Skin infestations
Lice or scabies (or the more severe crusted/norwegian form in immunosuppressed)
Tropical skin infections
Leishmaniasis or leprosy
Factors which predispose to cutaneous infections
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
Impetigo
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.
Staphylococcus scalded skin syndrome (SSSS)
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)
Erysipelas
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
Cellulitis
Bacterial infections of the skin spreading to the subcut fat
Most common on face and lower limbs
Can be staph or strep.
Treatment of Bacterial skin infections
1g Amoxycillin TDS or Penicillin V 1g daily for 2 weeks
If recurrent need long term antibiotics. 2nd line for cellulitis is flucloxaxillin. D
Folliculitis
Inflammation in hair follicles usually due to staph aureus – can occlude the follicules leading to pustules. Management –> aseptic washes, topical antibiotics or oral fluclokacillin
Carbuncles
infection in both follicle and subcutaneous tissue
Human papilloma virus (HPV)
Skin and genitals worse effected – major carcinogenic effect
Produces warts – treat with cryotherapy, salicytic acid or CO2 laser curettage
Herpes simplex virus (HSV)
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
Varicella Zoster virus (VZV)
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)
Molluscum contagiosum
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
Candida skin infections
Hyphae forming yeast commensal - creamy white patches on mucus membranes, angular chelitis
Mainly problem in immunosuppressed (HIV or babies)
Treat iwth fluconazole or nystatin
Tinea - Corporis/capitis/pedis (Ringworm)
Annular, demarcated lesions with a palpable edge
Can have scaling, pustules or vesicles
Treat with terbinafine or ketoconazole
Scabies
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
Lice
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
Leishmaniasis
Can effect skin, mucus membranes or organs
2million cases/yr in 88 countries
Sandfly vector bites –> nodule –> ulcer
Treat with pentovalent antimonials (Na stibogluconate)
Leprosy
Can be tuberculoid or lepromatous disease depending on immunological status
Mechanism of transmission unknown
Treat with Dapsone, rifampicin, clofazimine
Molluscum Contagiosum
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.
Progression of Molluscum contagiosum
Incubation is usually 2-7wks but can be up to 6months. Lesions may be present up to 12months and usually self-limit within 18months.
Fungal Nail infections (Onychomycosis)
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).
Systemic causes of Pruritus
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
Athletes Foot
Tinea pedis - caused by trichophyton fungus. Causes scaling, flaking and itching between the toes. treat topical imidazole, undecenoate or terbinafine.
Painful blistering rash
Probably shingles - not many things which cause pain and blistering.
Erythrasma
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.
