Drug Hypersensitivity due to Azathioprine with Elevated Procalcitonin

We present a case of azathioprine hypersensitivity presenting as sepsis with elevated procalcitonin in a 68-year-old man with myasthenia gravis. The patient presented with fever, chills, nausea, vomiting, and headache. He developed numerous 1 cm erythematous papules over his upper torso. Infectious workup including bacteriological tests and microbial cultures was negative and a skin biopsy was performed which revealed suppurative folliculitis with eosinophils, consistent with drug hypersensitivity. Notably, acute phase reactants including C-reactive protein and procalcitonin were elevated upon presentation, likely secondary to drug hypersensitivity.