Acquired Factor V Inhibitor with Hemorrhagic Symptoms after Prasugrel Hydrochloride Treatment.

Acquired factor V inhibitor (AFVI) is a rare coagulopathy. It may be triggered by specific antigens such as antibiotics. We herein report the first case of AFVI after treatment with prasugrel hydrochloride (prasugrel) in an 80-year-old male who underwent percutaneous coronary intervention because of angina pectoris 6 years ago and was initiated on aspirin and ticlopidine hydrochloride. He was switched from ticlopidine hydrochloride to prasugrel before undergoing percutaneous coronary intervention for myocardial infarction. Fifteen days later, he developed sudden nasal hemorrhage, hematuria, and systemic purpura. Coagulation tests revealed prolonged prothrombin time-international normalized ratio (11.35) and activated partial thromboplastin time (170 s). The coagulation factor profile revealed a decreased FV activity (1%). The Bethesda assay for FV inhibitor was positive. AFVI was diagnosed; prasugrel was immediately discontinued, and administration of recombinant activated factor VII and prednisolone were initiated. Hemorrhagic symptoms immediately disappeared; FV activity improved, and the FV inhibitor titer was normalized.