Several days ago, a 14-year-old boy suddenly became ill with abdominal pain, fever, and arthralgia. Within 12 hours, a rash developed that covered most of his trunk, arms, and legs but spared his face, palms, and soles. It quickly flared bright red; some lesions were tender to touch. The patient’s legs and scrotum became edematous, and he lost his appetite. The patient developed diarrhea, and bright red blood was seen in his stools.
He was taken to the local emergency department, where examination revealed a fever of 101.5°F, an elevated white blood cell count, and a small amount of blood in his urine. Stool cultures were ordered, and the patient was placed on an unknown antibiotic.
The next day, he consulted his pediatrician, who referred him to dermatology.
EXAMINATION
Today, the patient is afebrile and in no acute distress. He still has a florid rash on his trunk, arms, and legs consisting of very evenly distributed, purpuric lesions that average 3 mm in diameter. A few are palpable, and none are blanchable. A punch biopsy is performed, and an entire lesion is obtained and submitted for pathologic examination.
What is the diagnosis?