Visual Diagnosis

Presentation

A 6-year-old previously healthy boy presents to an urgent care clinic with the complaint of fever and several tender, erythematous, circular lesions on his skin. The child had been doing well until 2 days ago, when he developed the abrupt onset of subjective fever, frontal headache, nausea, and vomiting. Yesterday, he began complaining of pain over his left elbow. The skin over the elbow became progressively erythematous, with a small papule appearing that increased in size and started to blister. Overnight, the lesion ruptured and the parents noted several similar lesions starting to appear, one on the right shoulder and two others on the left chest. These lesions progressed similarly, all having ruptured by the time of presentation to the clinic.

Review of systems reveals decreased activity and mild fatigue. His appetite has been normal, with good intake of food and liquids. His urine output has not decreased, and his stool pattern has not changed. The rest of the review of systems is negative.

The boy's past medical history is unremarkable. He was born at term following an uncomplicated pregnancy. He had had no prior hospitalizations or surgeries, and apart from some occasional doses of acetaminophen during this febrile illness, he took no medications. His immunizations are up to date. The family history reveals no significant medical problems. No similar symptoms are present in family or social contacts. He has not traveled recently and has no exposure to animals.

Physical examination reveals a pleasant boy who is alert and cooperative but minimizes movement of his left arm. Vital signs include a temperature of 39.0°C, heart rate of 139 beats/min, respiratory …