Picture Quiz: A man with a mamillated rash and fever

A 59-year-old man presented with a painful rash on his face, neck, and extremities, with associated fever. The rash followed a URI 1 week before. He was treated with valacyclovir, without improvement. Exam: extensive papules and plaques with mamillated surface and a pseudovesicle quality. Labs: WBC normal, 77% neutrophils. Erythrocyte sedimentation rate elevated. What's the dx?