Erythema Flashcards
What causes erythema ab igne?
over exposure to infrared radiation.
A typical history would be an elderly women who always sits next to an open fire.
Features of erythema ab igne
- reticulated, erythematous patches with hyperpigmentation and telangiectasia.
Typical patient presenting with erythema ab igne
- elderly women who always sits next to an open fire.
What may develop if the cause of erythema ab igne is not removed?
May develop SCC
What is erythema multiforme?
- hypersensitivity reaction
- most commonly triggered by infections
Features of erythema multiforme
- target lesions
- initially seen on the back of the hands / feet before spreading to the torso
- upper limbs > lower limbs
- pruritus usually mild
Causes of erythema multiforme
- Viral - herpes simplex virus
- idiopathic
- bacteria: Mycoplasma, Strep
- Drugs: penicillin, sulphonamides, carbamazepine, allopurinol, NSAIDs, oral contraceptive pill,
- Connective tissue disease e.g. SLE
- Sarcoidosis
- Malignancy
What feature changes a diagnosis to erythema multiforme MAJOR?
Mucosal involvement
What is erythema nodosum?
- inflammation of subcutaneous fat
Features of erythema nodosum
- tender, erythematous, nodules
- MAINLY shins
- may also occur elsewhere (e.g. forearms, thighs)
How long does it normally take erythema nodosum to resolve? Do the lesions scar?
6 weeks
no scarring
Causes of erythema nodosum
infection
- strep, TB
systemic disease
- sarcoid, IBD, Behcet’s
malignancy/lymphoma
drugs
- penicillins, sulphonamides, COCP
Pregnancy
Features of erythrasma
- asymptomatic
- flat, slightly scaly, pink or brown rash
- usually found in the groin or axillae
What causes erythrasma
-overgrowth of the diphtheroid Corynebacterium minutissimum
What investigation findings can help diagnose erythrasma?
Examination with Wood’s light
= coral-red fluorescence.
