Erythema multiforme

Erythema multiforme (EM)
Erythema multiforme minor of the hands (note the blanching centers of the lesion)
Classification and external resources
Specialty	Dermatology
ICD-10	L51
ICD-9-CM	695.1
DiseasesDB	4450
MedlinePlus	000851
eMedicine	derm/137
MeSH	D004892
[]

Erythema multiforme (EM) is a skin condition of unknown cause; it is a type of erythema possibly mediated by deposition of immune complexes (mostly IgM-bound complexes) in the superficial microvasculature of the skin and oral mucous membrane that usually follows an infection or drug exposure. It is an uncommon disorder, with peak incidence in the second and third decades of life. The disorder has various forms or presentations, which its name reflects (multiforme, "", from + ). Target lesions are a typical manifestation. Two types, one mild to moderate and one severe, are recognized (erythema multiforme minor and erythema multiforme major).

The condition varies from a mild, self-limited rash (E. multiforme minor) to a severe, life-threatening form known as erythema multiforme major (or erythema multiforme majus) that also involves mucous membranes.

Consensus classification:

The mild form usually presents with mildly itchy (but itching can be very severe), pink-red blotches, symmetrically arranged and starting on the extremities. It often takes on the classical "target lesion" appearance, with a pink-red ring around a pale center. Resolution within 7–10 days is the norm.

Individuals with persistent (chronic) erythema multiforme will often have a lesion form at an injury site, e.g. a minor scratch or abrasion, within a week. Irritation or even pressure from clothing will cause the erythema sore to continue to expand along its margins for weeks or months, long after the original sore at the center heals.

Many suspected aetiologic factors have been reported to cause EM.

EM minor is regarded as being triggered by HSV in almost all cases. A herpetic aetiology also accounts for 55% of cases of EM major. Among the other infections, Mycoplasma infection appears to be a common cause.

Herpes simplex virus suppression and even prophylaxis (with acyclovir) has been shown to prevent recurrent erythema multiforme eruption.

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