Skin Infection Flashcards
What are the causes of infection?
- Bacterial
- Viral
- Fungal
- Infestations
What is this?
Cellulitis
- Bacterial infection of lower dermis and subcutaneous tissue
- Red, painful, swollen skin with poorly defined edge
- Usually unilateral
- Can be associated with systemic symptoms
- Commonly caused by Strep pyogenes and Staph aureus
- Discuss risk factors e.g. previous episode of cellulitis, diabetes, venous disease etc
What is this?
Erysipelas
- Affects upper dermis
- Usually caused by Group A beta haemolytic strep (Strep pyogenes)
- Affected skin has sharp raised border (cellulitis less well demarcated, and does not have such marked swelling)
- Red, firm and swollen, can be dimpled
- Treatment – penicillin antibiotic of first choice
Treatment of cellulitis
- Look for portal of entry
- Swabs +/- bloods
- Analgesia, fluid, elevation
- Treat co-existing skin conditions
- Uncomplicated cellulitis can be treated with oral antibiotics
- If severe cellulitis or systemic symptoms, IV antibiotics are needed
- Antibiotics based on local protocol or sensitivities
- Prolonged course may be required
What is this?
Impetigo
- Superficial bacterial skin infection
- Pustules and honey-coloured crusted erosions
- Most often caused by S aureus , also caused by group A strep (Strep pyogenes)
- Most common in children
- Usually affecting face and hands
- Single or multiple irregular crops
- Bullous vs non-bullous - bullous due to staph exfoliative toxins
What is this?
Boil aka furuncle
- S aureus
- May be associated cellulitis
- 10-20% Staph carriers – nose, armpits, groin
- Topical antiseptic / compress / oral abics / be aware of sepsis
- Carbuncle = collection of interconnecting boils.
-
Treatment of a furuncle
- Antibiotic ointment e.g mupirocin or fusidic acid
- Oral antibiotics
What is this?
Meningococcal rash
- Neisseria meningitidis
- Spreads to blood and brain causing meningocccemia and/or meningococcal meningitis
- Petechia and purpura, may be extensive
- Dx-blood culture and LP
- Rx-Penicillins
What is this?
Viral exanthem
- Exanthem – Widespread rash accompanied by systemic symptoms
- Common in childhood – e.g. chicken pox, measles, rubella, parvovirus b19 can present as such
- Various other viruses
- Drug reactions an important differential
What is this?
HSV (Herpes simplex)
Type 1 – usually orofacial
Type 2 – usually anogenital
After primary infection, recurrent infections can occur
Recurrent Type 1 HSV occurs most frequently on face esp lips – herpes simplex labialis
Dx – viral swabs for PCR
Rx – mild cases do not required Rx, severe cases may require antivirals e.g. aciclovir
What is this?
Eczema herpeticum
- Dissemination viral infection
- Most cases due to HSV
- Fever, clusters of painful, itchy blisters and punched out erosions
- Commonly a complication of atopic eczema
- Complicated by secondary bacterial infection
- Antiviral treatment, IV antivirals required if patient unwell or immunocompromised
-
What is this?
Shingles (herpes zoster)
What is this?
Varicella zoster
What is this?
Viral wart aka verruca
- Caused by HPV
- Common in children and in immunocompromised
- Hard keratinous surface
- Tiny dot can be seen at centre of each scaly spot – intracorneal haemorrhage
- Common on backs of fingers and toes
- Rx-salicylic acid, cryo
Explain fungal infections
- Superficial (common) and deep (rare, tropical)
- Superficial
- Dermatophytes (Tinea)
- Candida
- Yeasts
What is this?
Tinea
- Dermatophyte skin infection
- Name depending of body part affected
- Prefix tinea +body site
What is this?
Onychomycosis
Fungal infection of nails
- Can be caused by dermatophytes, yeasts, moulds
- commonly due to T Rubrum
- Ix-nail clippings for microscopy and culture
- Rx- topicals antifungals if limited usually needs oral
What is this?
Candidal intertrigo
Candida
- Intertrigo describes rash in body folds
- Candida often affects intertriginous areas typically inframammary
- Pink to bright red moist patches +/- satellite papules and pustules
What is this?
Tinea versicolour
Pityriasis versicolor
- Common yeast infection of the skin
- Pityriasis -scale appears similar to bran
- Versicolor-multiple colours
- Masselezia fungus
- Affects trunk, neck, arms
- Brown or pink patches, pale patches common in darker skin
- Asymptomatic, sometimes mildly itchy
Microscopy
Spaghetti and meatballs appearance – yeast and hyphae
What is this?
Seborrhoeic dermatitis
Seb derm
- Not infection
- Associated with proliferation of commensal Malassezia
- Its metabolites cause an inflammatory reaction
- Infantile seb derm
- Adult seb derm - scalp, face (creases around the nose, behind ears, within eyebrows) and upper trunk.
What is this?
Insect bite reaction
What is this?
Scabies
- Sarcoptes scabiei
- Parasitic mite that burrows under skin
- Causes an intensely itchy rash
- Worse at night disturbing sleep
- Burrows – grey irregular tracks
- Look in webspaces of fingers and toes, palms, wrists
- Also found on elbows, nipples, buttocks, penis, soles
- Rarely involves face and scalp
- Can develop a generalised rash which is a hypersensitivity reaction few weeks after
What is this?
Different presentations of scabies rash
Acropustulosis ( sterile pustules on palms and soles in babies)
Erythematous papules on trunk and limbs
Treatment of scabies
- 5% permethrin cream applied all over skin and left on for 8-10 hours
- Oral ivermectin 200mcg/kg
- Treatment repeated a week later to kill newly hatched mites
- Identify and treat contacts
- Launder bed linen, towels, clothing and clean rooms
- Seal items that cannot be washed in plastic bag for a week
- Itching may persist up to 6 weeks
