Erythema multiforme

Question 1

Define

Answer 1

an acute hypersensitivity reaction of the skin and mucous membranes. Stevens-Johnson syndrome is a severe form with bullous lesions and necrotic ulcers

Question 2

Causes

Answer 2

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:

• Drugs - e.g. sulphonamides, penicillin, phenytoin
• Infection - e.g. HSV, EBV, adenovirus, chlamydia, histoplasmosis
• Inflammatory - e.g. rheumatoid arthritis, SLE, sarcoidosis, ulcerative colitis
• Malignancy - e.g. lymphomas, leukaemia, myeloma
• Radiotherapy

Question 3

Epidemiology

Answer 3

Any age group

Mainly in CHILDREN and YOUNG ADULTS

TWICE as common in MALES

Question 4

Symptoms

Answer 4

Non-specific prodromal symptoms of upper respiratory tract infection

Sudden appearance of itching/burning/painful skin lesions

Skin lesions may fade leaving pigmentation

Question 5

Signs

Answer 5

• 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

Stevens-Johnson syndrome is characterised by:

• Affecting > 2 mucous membranes (e.g. conjunctiva, cornea, lips, mouth, genitalia)
• Systemic symptoms (e.g. sore throat, cough, fever, headache, myalgia, arthralgia, diarrhoea/vomiting)
• Shock (hypotension and tachycardia)

Question 6

Investigations

Answer 6

Usually unnecessary - erythema multiforme is very much a clinical diagnosis

Bloods

• High WC, eosinophils, ESR/CRP

Imaging - exclude sarcoidosis and atypical pneumonia

Skin biopsy - histology and direct immunofluorescence if in doubt about diagnosis