What Is Your Diagnosis? Urticaria Multiforme

A 15-month-old boy presented to his pediatrician and was noted to have increased fussiness, oral thrush, and right-sided otitis media. He was started on nystatin and a 14-day course of oral amoxicillin. One day after the final dose of amoxicillin, he developed several erythematous targetoid macules and patches with dusky purple centers on his face and chest. Two days later he was brought to the emergency department with a fever (temperature, 38.92°C); edema of his hands and feet; and spread of the cutaneous eruption to involve his trunk, extremities, and face.