Derm Dx: A sudden, blotchy rash on the cheeks

The patient is an 18-month-old child who presents for evaluation of a rash affecting both cheeks. The onset was sudden and not preceded by trauma or exposure to excessive heat. The child is afebrile and in no acute distress. He received a brief course of amoxicillin approximately 4 weeks ago for a respiratory illness. Examination revealed well-demarcated zones of erythema, ...