Transient FV inhibitor of unknown origin in difficult clinical situation

Abstract

Acquired Factor V inhibitors are a rare condition, associated frequently with at times severe bleeding. Patients can show no symptoms and in exceptional cases thrombosis can be reported. In this article we report two cases of acquired FV inhibitors associated with thrombosis. We systematically reviewed the literature on FV inhibitors and thrombosis. A patient had acquired FV inhibitors and thrombosis. He had no bleeding and was treated with anticoagulant. Despite initial improvement, he died from legionaire’s disease. The second patient had septicemia, acquired FV inhibitors and deep vein thrombosis. The patient’s condition improved with anticoagulation and antibiotic therapy. Ten case reports were considered in the systematic review. The median age at admission was 67. Seven patients had bleeding episodes. The median peak inhibitor titer was 2.7 BU (0.62-8) while the median FV activity was 2% (1-75). Except for 2 patients, all recovered. FV has two activities: a procoagulant action activating prothrombin, as well as an anticoagulant action activating protein C. This property could be associated with thrombosis activity. Inhibitor could also have a through effect on activated protein C. In our study, because of underlying diseases, it was not possible to clearly demonstrate that inhibitors give thrombosis. Immunosuppressive therapies were administered in cases of severe bleeding. Heparin seemed efficient for thrombosis without major bleeding. The prognosis of acquired FV inhibitors appeared to be related to the underlying disease.