Erythema multiforme (EM) is clinically characterized by a "minor" form and a "major" form. The latter is known as the Stevens-Johnson syndrome. Infections (particularly herpes simplex and Mycoplasma pneumoniae) and drugs seem to predispose toward the development of EM. The pathogenesis is poorly understood. The treatment is supportive. Prognosis varies with the severity of the eruption. Recurrences are commonly seen.