Derm Dx: Unilateral pink rash on the left side

A 5-year-old boy presents to the dermatology clinic with a rash around his left armpit, left torso and left upper arm that his mother reports has been present for seven days.

The patient had surgery several weeks prior to rash onset, which consisted of an incision on the left upper trunk to place a nerve stimulator. During surgery, the patient’s skin ...