erythema multiforme (EM) /mul′tifôr″mē, mo͝ol′tēfôr″mā/ , any of three major clinical syndromes characterized by lymphocytic infiltrates in the skin that cause keratinocyte necrosis. The patient may experience polymorphous eruption of skin and mucous membranes. Macules, papules, nodules, vesicles or bullae, and target (bullseye-shaped) lesions are seen. The three major classifications of erythema multiforme are EM minor, EM major, and pure plaque toxic epidermal necrosis. EM minor is an acute form of the disease, characterized by three-ring target lesions on the extremities. Symptoms often follow an infection of herpes simplex. The patient may have raised lesions but no fever and no blistering. EM major is characterized by the presence of target lesions, blistering, and detachment of the skin and mucous membranes. EM major also tends to follow herpes simplex virus infections. Plaque toxic epidermal necrolysis may not be associated with target lesions. However, the condition is associated with detachment of large sheets of skin. It is generally drug induced. Definitive and preventive treatment depends on finding the specific cause. Supportive treatment includes the normalization of electrolytes, hydration, and topical steroids and emollients.
