Derm Dx: A diffuse erythematous rash that blanches with pressure

An 8-year-old child presents with a diffuse erythematous made up of punctate popular elevations the size of pinheads that blanche with pressure. The rash began with flushing of the cheeks and forehead and rapidly spread to the trunk and extremities, where it is most marked on the inguinal, axillary, antecubital and abdominal areas.

Rash onset occurred about one day after ...