A 46-year-old man comes to the physician for a 2-day history of body rash. He has hypertension managed with hydrochlorothiazide. He was started on allopurinol one week ago for recurrent podagra. Physical examination shows a diffuse maculopapular rash on the trunk and arms. Laboratory studies show:
Hemoglobin 14 g/dL
Serum WBCs 8,000/μL
Platelets 190,000/μL
Urine RBCs 0-2/hpf
Urine WBCs 120/hpf
Urine protein 1+
Which of the following is the most likely diagnosis?
