Erythema Multiforme

Abstract

Erythema multiforme (EM) has been divided into a minor (simplex) form and a major (bullous) form. The minor form is additionally subdivided into papular and vesiculobullous variants, and all three have been considered a continuum of the same process. Histologically, each shows varying degrees of dermal and epidermal inflammation and injury. The clinical manifestations are determined by both the intensity of the damage and the relative amount of injury to each layer. Histologic gradations show a continuum that parallels the clinical findings. The major variant is also referred to by the eponyms “Stevens-Johnson syndrome” (prominent skin and mucous membrane lesions with systemic signs) or “Fuchs syndrome” (prominent prolonged eye and oral involvement). Recent publications challenge the concept of a continuum and propose a division of erythema multiforme minor and erythema multiforme major into separate entities with different provoking causes. Overlap cases are reported, however, and until the pathogenesis of each is fully understood, the value of such a separation remains unclear. EM major shares some clinical and pathologic features with toxic epidermal necrolysis. This is a catastrophic illness with a 30 to 40% mortality rate.