Dermatology: Skin Infections Flashcards
State 4 types of skin infection & examples for each
- Bacterial: cellulitis, impetigo, folliculitis
- Viral: herpes simplex, chicken pox, shingles, viral warts, molluscum contagiosum
- Fungal: candidiasis, dermatophytes
- Parasitic/infestations: scabies, head lice
What is cellulitis?
Acute bacterial infection of the dermis and deep subcutaneous tissue/hypodermis
*NOTE: hypodermis also referred to as subcutaneous tissue, subcutis etc..
State some risk factors for developing cellulitis
- Trauma
- Insect bites
- Ulcers
- Tinea pedis (athlete’s foot)
- Venous insufficiency
- Lymphoedema
- Diabetes
- Obestiy
State the 2 most common causative organisms of cellulitis
- Streptococcus pyogenes (group A Streptococcus)
- Staphylococcus aureus
State signs & symptoms of cellulitis
Symptoms commonly found unilaterally on extremities or on face:
- Spreading erythema (with poorly defined margin)
- Pain
- Oedema/swelling
- Warm to touch
- Golden yellow crust may be present (indicated Staphylococcus aureus infection)
- Fever
- Malaise
May also see evidence of of blisters, ulcers, lymphangitis, lymphadenopathy
Discuss what investigations you would do if you supect a pt has cellulitis, include:
- Bedside
- Bloods
- Imaging
Bedside
- ?skin swab or aspirate
Bloods
- FBC: leucocytosis
- CRP: raised in inflammation/infection
- ESR: raised in inflammation/infection
- U&Es: baseline renal function to allow sensible antibiotic choice
- Blood culture & sensitivities: find causative organism
Imaging
- ?Ultrasound, x-ray or MRI: only if uncertain about diagnosis/suspect underlying abscess or necrotising fasciitis
What classification is used to guide the management of cellulitis; describe this classification
Eron Classification
- Class I — there are no signs of systemic toxicity or uncontrolled comorbidities.
- Class II — the person is either systemically unwell or systemically well but with a comorbidity (for example peripheral arterial disease, chronic venous insufficiency, or morbid obesity) which may complicate or delay resolution of infection.
- Class III — the person has significant systemic upset (such as acute confusion, tachycardia, hypotension), or unstable comorbidities that may interfere with a response to treatment, or a limb-threatening infection due to vascular compromise.
- Class IV — the person has sepsis or a severe life-threatening infection, such as necrotizing fasciitis.
Discuss the management of cellulitis
- Supportive care (e.g. rest, leg elevation, sterile dressings, analgesia)
-
Antibiotics (choice depends on Eron classification):
- Class I: oral flucloxacillin- manage as outpatient
- Class II: IV flucloxacillin- may be suitable for 48hr hosp admission
- Class III: IV flucloxacillin- hosp admision
- Class IV: IV flucloxacillin- hosp admission.
- Surgery may be required for pts with class IV cellulitis
- Identify and manage and underlying risk factors
- Prophylaxis is cellulitis is recurrent (2 or more episodes at same site)
Flucloxacillin is usually first line antibiotic for cellulitis; state some other antibiotics which may be used
- Co-amoxiclav (if infection around nose or eyes “danger triangle”)
- Clindamycin
- Clarithromycin (if penicillin allergic)
- Vancomyin (if MRSA may be causative organism)
State some potential acute complications of cellulitis
- Necrotising fasciitis
- Myositis
- Subcutaneous abscess
- Septicaemia
State some potential chronic complications of cellulitis
- Lymphoedema
- Recurrent cellulitis
- Chronic ulcer
Prophylaxis is given for pts with recurrent cellulitis (two or more episodes at same site); what antibiotics are used in cellulitis prophylaxis? (2)
Penicillin V or erythromycin for up to 2 years.
What is erysipelas?
What is the treatment?
Erysipelas is a distinct form of superficial cellulitis (bacterial infection of dermis & upper subcutaneous tissue). It is raised and sharply demarcated from uninvolved skin. Commonly involves face.
Treatment: flucloxacillin
For impetigo, discuss:
- Cause
- Who common in
- Whether it is contagious
- Two different types
- Superficial skin infection most commonly caused by Staphylococcus aureus bacteria and less commonly by Streptococcus pyogenes. NOTE: bullous impetigo ALWAYS caused by S.aureus
- Common in children particularly in warm weather
- Contagious so keep off school (spread vis direct contact with discharge from lesions)
- Non-bullous and bullous
For non-bullous impetigo, discuss:
- Presentation
- Management
Presentation
- Typically around nose or mouth
- Exudate gives ‘golden crust’
Management
- If localised and pt not at risk of complications or systemically unwell: antiseptic cream (e.g. hydrogen peroxide 1%)
- Alternatively, topical fusidic acid
- If suspect fusidic acid resistance, topical mupirocin
- Extensive disease: oral flucloxacillin or erythromycin if penicillin allergic
Exclude from school until lesions crusted and healed (as spread is via discharge from lesions) or 48hrs after commencing abx treatment
For bullous impetigo, discuss:
- Pathophysiology
- Presentation
- Who more common in
- Treatment
- Staphylococcus aureus bacteria produce epidermolytic toxins that break down protein holding skin cells together resulting in formation of fluid filled vesicles. These grow then burst to form golden crust. Lesions may be painful & itchy.
- Presentation: see above, common to have systemic symptoms e.g. fever
- More common in neonates & children <2yrs
- Management:
- Antibiotics- flucloxacillin PO or IV dependent on how well/unwell and risk of complications
- Advise that must stay off school until all lesions crusted over and healed or had 48hrs abx
For folliculitis, discuss:
- What it is
- Potential causes
- Presentation
- Management
- Inflammation of hair follicle(s)
- Causes
- Bacterial infection (most commonly S.aureus)
- Fungal infections
- Shaving
- Topical corticosteroids
- Re/in-growing hairs (and link to restrictive or tight clothing)
- Presentation:
- Erythematous papules or pustules around hair follicles
- Management:
- Usually self-limiting (general advice e.g. wash regularly with antibacterial soaps, loose clothing, shaving technique)
- Skin swab if recurrent
- If not clearing & positive swab…. antibiotics, antivirals, antifungals etc
Describe typical presentation of shingles
- Prodromal period:
- Burning pain over dermatome for ⅔ days
- Systemic symptoms e.g. fever, headache, lethargy
- Rash:
- Erythematous
- Starts macular then vesicular
- Well demarcated by dermatome & doesn’t cross midline
- T1-L2 most commonly affected
For molluscum contagiosum, discuss:
- Causative organism
- Presentation
- Management
- Viral skin infection caused by molluscum contagiosum virus
- Presentation:
- Small, flesh coloured papules with central dimple
- Typically occur in crops in a local area
- Contagious (direct contact or sharing items e.g. towels)
- Management:
- Reassurance and education regarding transmission. Usually resolves without treatment but can take up to 18 months
- If extensive lesions or lesions in problematic areas (e.g. eyelids, anogenital) refer to specialist for further treatments e.g. topical KOH, benzoyl peroxide, cyrotherapy
For viral warts, discuss:
- What they are
- Who common in
- Transmission
- Risk factors
- Different subtypes and presentation
- Papillomas (remember papilloma is a benign epithelial tumour) caused by HPV
- Common in childhood
- Spread via direct contact or via environment
- Risk factors: immunosupression, walking bare foot in public/shared spaces, biting nails etc…
- Subtypes & presentation:
- Plantar warts: thick hyperkeratotic plaques beneach pressure points on sole
- Verruca vulgaris: hyperkeratotic papules often on hands
- Planar warts: flat topped papules commonly occuring on face
- Condyloma acuminata (anogenital warts): cauliflower like plaques over anogential area
** Presence of thrombosed capillaries especially after paring is charcteristic of viral warts
What is meant by dermatophytosis?
Superficial fungal infection of keratinised tissues caused by dermatophytes. Dermatophytes are a specific group of fungi known as ring worms or tineas. Various names dependent on location of fungal infection:
Discuss management of candida skin infections
- Infection localised & pt not immunocompromised: topical imidazole e.g. clotrimazole
- If infection widespread, person immunocompromised or topical treatment ineffective: oral fluconazole (>16yrs)
- If inflammation & itch problematic: consider mild corticosteroid cream
For pityriasis versicolor, discuss:
- What is is
- Aetiology/pathophysiology
- Epidemiology
- Supeficial fungal infection of skin caused by yeasts of the genus Malassezia (Malassezia furfur). They are normal skin flora but can cause disease when converted to thei pathogenic hyphal form
- Common in teens & young adults (due to increased sebum production) and more common in tropical countries and in summer
Discuss how pityriasis versicolor presents
- Well demarcated thin plaques with fine scaling
- Plaques may be hyperpigmented, hypopigmented or erythematous
- Usually involves torso (can involve face)
- Can become confluent & widespread
- Post-inflammatroy pigmentary changes may persist for months despite eradication of infection
For scabies,
- Causative organism
- Presentation
- Management
- Mites called Sarcoptes scabei that burrow under skin and lay eggs leading to further infection
- Presentation:
- Itchy
- Small red spots
- Track marks/linear burrows
- Commonly in finger webs but may affect face & scalp in infants
- Management:
- Lifestyle: avoid close contact with others, launder any clothing/bedding/towels on high temp on first day, hoover carpets & furniture
- First line= permethrin 5% cream (apply to whole body when skin is cool and leave on for 8-12hrs then wash off. Repeat 1 week later. ALL HOUSEHOLD & CLOSE PHYSICAL CONTACTS SHOULD BE TREATED)
- Can give crotamiton cream & sedating antihistamines at night to help sleep
- If have crusted scabies (more common in immunosuppressed- especially HIV) then PO ivermectin
