Erythema Multiforme

Question 1

What is Erythema Multiforme?

Answer 1

Acute hypersensitivity inflammatory reaction of the skin + minimal mucous membrane involvement

Question 2

Describe the pathophysiology of Erythema Multiforme

Answer 2

Degeneration of basal epidermal cells
Development of vesicles between cells in the basement membrane
Lymphocytic infiltrate around blood vessels + at the dermo-epidermal junction
50% cases idiopathic

Question 3

List 5 precipitating factors and examples of each for Erythema Multiforme

Answer 3

Infection: HSV, Mycoplasma pneumonia, HIV
Drugs: sulphonamides, penicillin, phenytoin
Inflammatory: RA, SLE, sarcoidosis, UC
Malignancy: lymphomas, leukaemia, myeloma
Radiotherapy
Pregnancy

Question 4

Describe the epidemiology of Erythema Multiforme

Answer 4

Any age group
Mainly in CHILDREN + YOUNG ADULTS
M > F

Question 5

List 3 symptoms of Erythema Multiforme

Answer 5

Non-specific prodromal sx of URTI (fever, aches)
Sudden appearance of itching/ burning/ painful skin lesions
Skin lesions may fade leaving pigmentation

Question 6

List signs of Erythema Multiforme

Answer 6

Target “bull’s eye” lesions with a rim of erythema surrounding a paler area
Vesicles/ bullae
Urticarial plaques
Lesions are often symmetrical + distributed over the extremities inc. palms, soles + extensor surfaces

Question 7

What investigations are required for Erythema Multiforme?

Answer 7

Usually unnecessary (clinical dx)
Bloods: High WCC, eosinophils, CRP 
Imaging: exclude sarcoidosis + atypical pneumonia  
Skin biopsy: histology + direct immunofluorescence if in doubt about dx

Question 8

Which condition is Erythema Multiforme similar to, but less severe than?

Answer 8

Steven-Johnson syndrome

Causes systemic symptoms + shock