Derm Dx: Itchy rash on the trunk

A 60-year-old white patient, admitted to the hospital for a congestive heart failure exacerbation, complains of extremely itchy papules on his chest and back. The eruption started a few days after admission, after which the patient been vigorously scratching.

Since hospital admission the patient has been receiving intravenous furosemide. His home medications include furosemide, potassium chloride, simvastatin, metoprolol and ...