A 20-year-old man developed expanding red papules and plaques on his hands, arms, legs, and feet following an episode of cold sores. Scattered papules on his lips and oral mucosa became eroded and crusty. He was able to eat and drink with some difficulty. The eruption began to heal by the end of the week. Erythema multiforme (EM) is an acute hypersensitvity syndrome that may be caused by viruses (especially HSV), a number of drugs, immunizations, foods, bacterial infections, and other triggers. The rash may occur on any part of the body but typically appears on the dorsum of the hands and feet and the extensor surfaces of the arms and legs. EM minor is self-limiting. The eruption typically continues in crops that last 1-3 weeks. Systemic manifestations may include low-grade fever, malaise, and myalgia. Half of affected individuals develop at least a few oral and/vermillion border lesions.
2-3 cm round annular red plaques with dusky central bullae