Skin Infections + Infestations Flashcards
What are the most common bacterial skin infections?
20% of outpatient derm visits
- Impetigo
- Folliculitis
- Cellulitis
- Erysipela
- Syphilis
- Leprosy
- Rickettsial diseases
What is the most common ( and v contagious) bacterial infection in children?
Impetigo
Predisposing factors for impetigo?
Warm temp, high humidity
Poor hygiene
Skin trauma
What bacteria most commonly cause impetigo?
Staph aureus (to a lesser degree Strep pyogenes)
What is the clinical presentation of impetigo?
Macule rapidly becomes vesicle then pustule then erosion with ‘honey-coloured’ yellow crust and rapid extension to surrounding skin
How is impetigo treated?
Local wound care
Topical abx
What is folliculitis?
Infection of the hair follicule
What bacteria most commonly causes folliculitis?
Staph aureus
Predisposing features of folliculitis?
Occlusion Maceration + hyperhydration Shaving/waxing Topical corticosteriods Diabetes
What areas does folliculitis affect?
Face, chest, back, axillae, buttocks
How to identify causative organisms?
Bacterial cultures
Treatment for folliculitis?
Antibacterial washes
Antibacterial ointments
What is erysipelas?
Infection of the dermis w lymphatic involvement, most commonly caused by group A strep
What groups of people does erysipelas affect?
V young
Elderly
Debilitated
Those with lymphoedema/chronic cutaneous ulcers
Clinical presentation of erysipelas?
Erythema with well defined margins
Affected skin is hot, tense, indurated
Face, lower extremities
May have fever, chills, malaise, nausea
Diagnosis is clinical, but what could lab results show that contribute?
Elevated leukocyte count w left shift
Treatment for erysipelas?
10-14 day course of penicillin
What is cellulitis?
Infection of the deep dermis and subcutaneous tissue caused most commonly by Strep pyogenes or Staph aureus
Predisposing factors for cellulitis?
Lymphoedema Alcoholism Diabetes mellitus IV drug abuse Peripheral vascular disease
How does cellulitis present? (4 words for affected area)
Affected area = rubor, calor, dolor, tumor
Lesion has ill-defined, non-palpable borders
Children: H+N; adults: extremities
How is cellulitis treated?
Abx (depending on systemic symptoms and gravity, also risk factors)
What is syphilis?
Complex sexually transmitted infection
What bacteria causes syphilis?
Treponema pallidum
What is the time frame of presentation of syphilis?
Episodes of active disease occur, followed by latent periods
What is the danger if syphilis is left undiagnosed?
Tertiary syphilis can develop years later and cause a variety of problems affecting the brain, eyes, heart and bones
How does primary syphilis present?
Painless small single ulcer where he infection has entered (around genitals, anus or mouth) and may go unnoticed (known as chancre)
Heals in 4-8 weeks w/o treatment and 1-2 weeks w treatment
When does secondary syphilis occur?
3 weeks to 3 months after 1st stage
How does secondary syphilis present?
Widespread skin rash
May be subtle or appear as rough, red/reddish brown papules/patches
Typically on trunk/palms + soles
Not itchy
How does tertiary syphilis present?
Solitary granulomatous lesions (gummas) may be on skin, in mouth and throat/occur in bones
Brain, spinal cord, heart, liver, eyes may be affected
What tests can be done for syphilis?
Non-specific non-treponemal tests (VDRL)
Specific anti-treponemal antibody tests (TTPA)
Treatment of syphilis?
Penicillin by injection depending on stage of disease
What are the most common viral skin infections?
Herpes simplex Chicken pox Shingles Viral warts Molluscum contagiosum
How does HSV-1 present?
Most commonly sores around mouth
Present in approx 90% of individuals between 20-40 yrs
How does HSV-2 present?
Most commonly genital infection (associated with sexual activity)
How are the sores in herpes described?
V sore areas with erythematous base, with vesicles followed by pustules and ulcerations
What does the antiviral therapy depend on?
Type
What virus is chicken pox caused by?
Varicella-Zoster Virus (VZV)
What else does VZV cause? Is it related to chicken pox?
Shingles (herpes zoster)
Yes, shingles is the reactivation of latent varicella
What is chicken pox?
Highly contagious viral infection that causes an acute fever and blistered rash, mainly in children
How is chickenpox spread?
Airborne respratory droplets from an infected person’s coughing/sneezing, or through direct contact with fluid from open sores
How is the development of lesions in chickenpox described?
Red macules -> vesicles -> pustules -> crusts
Starts which vesicle on top of erythema - ‘dew drops on a rose petal’ - v characteristic
How is chickenpox treated?
Symptomatics
Calamine lotion
What is shingles?
Localised, blistering and painful rash caused by reactivation of varicella-zoster virus (VZV)
How is shingles characterised?
Dermatomal distribution
Why does shingles have a dermatomal distribution?
Blisters are confined because VZV remains dormant in specific dorsal root ganglia nerve cells in the cells
Complications of shingles?
Infection
Post-herpetic neuralgia
How is shingles treated?
Keep area clean to prevent infection
Pain relief and rest
What virus causes viral warts?
Human papillomavirus
What are the lesions in viral warts described as?
Hyperkeratotic papules (looks like cauliflower - typical)
Thick hyperkeratotic plaques
When grouped - ‘mosaic’
Treatment for viral warts?
Most resolve spontaneously
Salicylic acid
Cryotherapy
When should viral warts patient be referred to secondary care?
Diagnostic uncertainty
Immunocompromised patients
Large/extensive warts
Who is mainly affected by molluscum contagiosum?
Infants
Children <10 yrs
Warm climates/overcrowded environments
What virus causes molluscum contagiosum?
Poxvirus (poxviridae family)
What are the lesions like in molluscum contagiosum?
Firm, umbilicated pearly papules w waxy surface
Common in skinfolds/genitals
How is MC treated?
Curettage (try to avoid as theres loads)
Liquid nitrogen
Chemovesicants
Can go away on own
What are the 3 commonest fungal skin infections?
Dermatophytosis
Candidiasis
Pityriasis versicolor
Dermatophytosis = ringworm = tinea; what are the types?
Tinea corporis (general) Tinea cruris (groin) Tinea capitis (scalp) (only one that is common in children) Tinea pedis (foot) Tinea unguium (nail)
What does ringworm look like?
Circular lesion; ‘wave’ of fungus going through healthy skin - redder at outline than middle
Predisposing factors of mucocutaneous candida infections?
Diabetes Occlusion (e.g. nappies) Hyperidrosis Broad spectrum abx Immunosuppression
What fungus causes candida infections?
Candida albicans
What does candida infection present as?
Erythematous patches often accompanied by satellites pustules Intertriginous zones (submammary, inguinal creases, finger spaces) and nappy area in infants
Treatment of candida?
Remove predisposing factors
Topical antifungals
Oral antifungal in some cases
What fungus causes pityriasis versicolor?
Malassezia sp
What do lesions of PV look like?
Multiple oval round patches w mild scale
More info on PV?
Increased incidence in adolescents and preference for sebum-rich areas of skn
High temperatures and humidity, oily skin, excessive sweating
Treatment of PV?
Topical antimycotic (shampoos, creams)
What are the 2 skin infestations?
Scabies
Headlice
What mite causes scabies?
Sarcoptes scabei
How is scabies transmitted?
Direct close contact
Predisposing factors for scabies?
Overcrowding
Delayed treatment
How can scabies be diagnosed?
Skin scraping
Burrows visualisation
Scabies is v v itchy, when is the itch characteristically more severe?
At night (disturbing sleep)
Where does scabies affect?
Trunk and limbs; sparing scalp
How do scabies burrows appear?
0.5–1.5 cm grey irregular tracks in the web spaces between the fingers, on the palms and wrists
Treatment of scabies?
Antiscabietic topical treatment in patient and close contacts, repeat after 1 week
Oral meds in some cases
What do head lice cause?
Itch and irritation in scalp
How do headlice present?
Itchy scalp
Nits can be seen once eggs have hatched, as adherent white grains on hair shaft
Red-brown spots caused by excreted digested blood
Treatment for headlice?
At least 2 applications of an insecticide and/or physical methods (combs)
Treat all members of fam
Inform day care/school
