Erythema Multiforme Flashcards
Definition
An acute hypersensitivity reaction of the skin and mucous membranes.
Stevens-Johnson syndrome is a severe form with bullous lesions and necrotic ulcers
Aetiology
· Degeneration of basal epidermal cells
· Development of vesicles between cells in the basement membrane
· Lymphocytic infiltrate around the blood vessels and at the dermo-epidermal junction
· A precipitating factor is only identified 50% of the time
Precipitating factors
o Drugs - e.g. sulphonamides, penicillin, phenytoin
o Infection - e.g. HSV, EBV, adenovirus, chlamydia, histoplasmosis
o Inflammatory - e.g. rheumatoid arthritis, SLE, sarcoidosis, ulcerative colitis
o Malignancy - e.g. lymphomas, leukaemia, myeloma
o Radiotherapy
Epidemiology
· Any age group
· Mainly in CHILDREN and YOUNG ADULTS
· TWICE as common in MALES
Presenting symptoms
· Non-specific prodromal symptoms of upper respiratory tract infection
· Sudden appearance of itching/burning/painful skin lesions
· Skin lesions may fade leaving pigmentation
Signs on physical examination
· Classic target (bull’s eye) lesions with a rim of erythema surrounding a paler area
· Vesicles/bullae
· Urticarial plaques
· Lesions are often symmetrical and distributed over the arms and legs including the palms, soles
and extensor surfaces
Signs on physical examination (Stevens-Johnson Syndrome)
o Affecting > 2 mucous membranes (e.g. conjunctiva, cornea, lips, mouth, genitalia)
o Systemic symptoms (e.g. sore throat, cough, fever, headache, myalgia, arthralgia, diarrhoea/vomiting)
o Shock (hypotension and tachycardia)
Investigations
· Usually unnecessary - erythema multiforme is very much a clinical diagnosis
· Bloods
o High WC, eosinophils, ESR/CRP
· Imaging - exclude sarcoidosis and atypical pneumonia
· Skin biopsy - histology and direct immunofluorescence if in doubt about diagnosis
