Clinical features, diagnosis, and treatment of erythema multiforme: a review for the practicing dermatologist.

Erythema multiforme (EM) is an uncommon, immune-mediated disorder that presents with cutaneous or mucosal lesions or both. In herpes simplex virus (HSV)-associated EM, the findings are thought to result from cell-mediated immune reaction against viral antigen-positive cells that contain the HSV DNA polymerase gene (pol). The target lesion, with concentric zones of color change, represents the characteristic cutaneous finding seen in this disorder. Although EM can be induced by various factors, HSV infection continues to be the most common inciting factor. Histopathologic testing and other laboratory investigations may be used to confirm the diagnosis of EM and to differentiate it from other clinical imitators. Imitators of EM include urticaria, Stevens-Johnson syndrome, fixed drug eruption, bullous pemphigoid, paraneoplastic pemphigus, Sweet's syndrome, Rowell's syndrome, polymorphus light eruption, and cutaneous small-vessel vasculitis. Because disease severity and mucosal involvement differ among patients, treatment should be tailored to each patient, with careful consideration of treatment risk vs benefit. Mild cutaneous involvement of EM can be managed primarily with a goal of achieving symptomatic improvement; however, patients with HSV-associated recurrent EM and idiopathic recurrent EM require treatment with antiviral prophylaxis. Inpatient hospitalization may be required for patients with severe mucosal involvement that causes poor oral intake and subsequent fluid and electrolyte imbalance. With this review, we strive to provide guidance to the practicing dermatologist in the evaluation and treatment of a patient with EM.