Acute Widespread Rash in a 9-month-old Boy

April 27, 2016
ReelDx
ReelDx

What is the cause of this erythematous rash that appeared suddenly and spread rapidly on the child's trunk and extremities?

A 9-month-old boy is seen for an acute, widespread erythematous rash with wheals appearing on trunk and extremities. The child is afebrile, appears well, and the mother reports the rash does not appear to be pruritic. She denies recent illnesses and sick contacts.

What does this rash look like to you?