Urticaria multiforme.

Urticaria multiforme is a benign cutaneous hypersensitivity reaction seen in pediatric patients that is characterized by the acute and transient onset of blanchable, annular, polycyclic, erythematous wheals with dusky, ecchymotic centers in association with acral edema. It is most commonly misdiagnosed as erythema multiforme, a serum-sickness-like reaction, or urticarial vasculitis. Since these three diagnoses represent distinct clinical entities with unique prognoses and management strategies, it is important that physicians distinguish urticaria multiforme from its clinical mimics in order to optimize patient care. By performing a thorough history and physical examination, the astute clinician can make the correct diagnosis and develop an appropriate, effective treatment plan while avoiding unnecessary biopsies and laboratory evaluations. The authors report a case of urticaria multiforme in a four-year-old girl in order to emphasize the distinctive morphological manifestations of this rare, albeit unique, disease seen in the pediatric population.