The diversity in clinical presentation of acquired factor V inhibitor. Two case reports.

摘要

Acquired inhibitors of specific coagulation factors are rare in clinical medicine. These antibodies bind and inactivate specific coagulation factors leading in most cases to an increased risk of severe bleeding. Among them, anti-factor VIII is the most frequently encountered. Inhibitors against factor V (FV) are much less frequent. Coagulation FV is a cofactor exerting central roles both in thrombin generation and in the protein C anticoagulant pathway. In contrast to other coagulation factor inhibitors, the clinical effect of FV inhibitor does not correlate well with its plasma levels. In a recent review of 126 published cases of patients with FV inhibitor, only 33% presented hemorrhagic manifestations. This inhibitor has been most frequently associated with bovine thrombin exposure . A FV inhibitor associated to a thrombotic risk has also been reported by Kalafatis et al. in a patient with severe thrombotic manifestations. The patient developed an antibody that recognized FV and induced protein C resistance when added to normal plasma. FV inhibitors have also been associated with major surgery, malignancies, autoimmune disorders, blood transfusion, bacterial infection, antibiotic therapy, acquired immunodeficiency syndrome, pregnancy as well as unknown precipitants [1, 3-6]. Their presence can result in significant morbidity and mortality if not recognized and treated promptly. In this report, 2 patients who developed FV inhibitors with similar FV activity but diverse clinical presentation are described.