Erythema Multiforme

Question 1

Define:

Answer 1

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

Question 2

Aetiology:

Answer 2

• Cause not fully understood – most likely a skin-directed immune reaction which occurs following exposure to a trigger in predisposed individuals. Type 4 hypersensitivity
• Changes that occur
o Degeneration of basal epidermal cells
o Development of vesicles between cells in the basement membrane
o Lymphocytic infiltrate around the blood vessels and at the dermo-epidermal junction

Question 3

Precipitating factors:

Answer 3

Drugs - e.g. sulphonamides (COMMON), NSAIDs, anti-convulsants, allopurinol

Infection - e.g. HSV (most common cause!), EBV, adenovirus, chlamydia, histoplasmosis and toxoplasmosis

Inflammatory - e.g. rheumatoid arthritis, SLE, sarcoidosis, ulcerative colitis

Malignancy - e.g. lymphomas, leukaemia, myeloma

Radiotherapy
o 50% of cases are idiopathic

Question 4

Epidemiology:

Answer 4

• Any age group
• Mainly in CHILDREN and YOUNG ADULTS
• TWICE as common in MALES

Question 5

Symptoms incl steven johnson syndrome:

Answer 5

• Non-specific prodromal symptoms of upper respiratory tract infection
• Sudden appearance of itching/burning/painful skin lesions
Few to hundreds of red papules (spots) which usually begin over back of feet and hands and spread upwards towards the trunk
Over time the papules evolve to plaques (raised patches) and then typical target shaped lesions – dusky red centre, paler area around this, then dark red ring around edge.
• Skin lesions may fade leaving pigmentation
• Steven Johnsons Syndrome – fever and mucosal involvement too (mouth, genital and eye ulcers)

Question 6

Signs:

Answer 6

• 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

Question 7

Signs of Steven Johnson syndrome:

Answer 7

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)

Question 8

Investigations:

Answer 8

• 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