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Erythema Multiforme

  • Erythema Multiforme (EM) is an acute, self-limited skin eruption with characteristic morphology that is typically triggered by certain infections and less commonly by drugs.
Etiology and Pathogenesis
  • The precise cause of EM is unknown but circulating immune complexes are suspected. The eruption is often preceded by primary or reactivated Herpes Simplex Virus infection or that of Mycoplasma pneumoniae. In many cases a particular infectious agent is not identified although a recent history of a febrile illness or URI may be uncovered.
Morphology and Clinical Consequences
  • Whatever the precise trigger, the lesions of EM develop acutely within 24-72hrs and appear as multiple characteristic, well-demarcated circular lesions with three distinct color zones that resemble a bulls eyes and thus are often referred to as "targetoid". However, atypical erythematous lesions can arise thus supporting the "multiforme" naming. Lesions are often pruritic or may give a burning sensation; however, self-resolve spontaneously.
  • Treatment of the underlying infection or avoidance of the precipitating drug will resolve EM.