Clinical Management of Erythema Multiforme in the Urgent Care Setting Urgent message: With the increasing use of medications, especially antibiotics, more and more patients are presenting to urgent care with erythema multiforme. Correct diagnosis and identification of the under- lying cause can result in rapid clinical resolution of the lesions. Shailendra Kapoor, MD However, the recent ten- dency has been to categorize SJS and TEN in a different category from EM. 1 SJS and TEN usually involve the torso, and the Nikolsky’s sign is usually positive; in EM, the torso is usually spared and the Nikolsky’s sign is usually negative. 2 The body surface area involved in TEN is greater than 30%, while in SJS and EM less than 10% of body area is involved. Introduction escriptions of erythema multiforme (EM) first ap- peared in the work of Al- bert and Bazin in 1822, but it was not until 1866 that von Hebra categorized these erythematous eruptions and labeled them “erythema exudativum multiforme.” To- day, we know that EM is more common in younger adults, especially men. There are two types of EM: EM minor and EM major. EM minor comprises nearly 70% of the cases. Most cases of EM minor resolve in one to three weeks, while EM major might take three to six weeks to resolve. Recurrences are more commonly seen in EM minor, but are rare in EM major. Traditionally, Stevens- Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) were included in the same spectrum as EM. w w w. j u c m . c o m © Bart's Medical Library / Phototake D Etiology and Pathogenesis Even though the exact pathogenesis of EM is not completely understood, it is thought to be caused by vi- ral, bacterial, or chemical triggers that initiate a hyper- sensitivity reaction. It may represent a type III immune complex-mediated hypersensitivity reaction, with a portion of the pathology arising from a type IV de- JUCM T h e J o u r n a l o f U r g e n t C a r e M e d i c i n e | M a y 2 0 0 7 11