Antibiotic-Induced Acquired Factor V Inhibitor

Abstract

Acquired factor V inhibitor is a rare condition with a variety of clinical manifestations that range from no bleeding symptoms to life-threatening hemorrhage or thromboembolic events. Treatment is determined by the clinical course and focuses on controlling the hemorrhagic event and decreasing the antibody titer if bleeding symptoms are present. We report herein a case involving a 70-year-old man who developed acquired factor V inhibitor after antibiotic administration (11-day course of ceftriaxone and successive 5-day course of piperacillin-tazobactam) for pneumonia. His condition was characterized by elevated prothrombin and activated partial thromboplastin times without bleeding events. Coagulation factor assays revealed undetectable factor V activity and a factor V inhibitor level of 3.29 Bethesda units. After cessation of the antibiotics, both the prothrombin and activated partial thromboplastin times gradually normalized.