Profound neutropenia associated with benzylpenicillin.

A 31-year-old white man with suspected aspiration pneumonia complicated by multiple pulmonary abscesses had profound neutropenia during a course of high-dose benzylpenicillin therapy for suspected bacterial endocarditis. Antigranulocyte antibodies were identified in the patient's serum. Leukopenia is an uncommon but potentially serious complication of therapy with this drug. We recommend weekly monitoring of blood counts during prolonged therapy with any beta-lactam antibiotic.