Advances in Acquired Hemophilia A

Abstract

Acquired Hemophilia A (AHA) is a rare, life-threatening bleeding disorder from autoantibodies against clotting factor VIII. These autoantibodies occur with increasing incidence with advanced age and are often associated with other medical conditions such as autoimmune diseases and malignancy. Not uncommonly, AHA presents as a new bleeding disorder in a person with prior thrombosis or thrombotic risk. Treatment of AHA focuses on managing and preventing bleeding, as well as immunosuppression with the goal to eradicate the autoantibody. Despite current treatment approaches, morbidity, and mortality are high due to complications from bleeding, immunosuppression, and underlying comorbidities. The most pressing needs to improved outcome for this disease are better bleeding prophylaxis in the outpatient setting and reduction of the need for intense immunosuppression. Because of the rare nature of this disease, there is limited prospective data and most treatment standards have been based on case series. The field has recently focused on improved diagnostics and advanced risk stratification, with a potential of tailoring the need and intensity of immunosuppression. Case reports of off label use of emicizumab, a factor FVIII mimetic approved for congenital hemophilia A, suggest emicizumab may provide effective and safe bleeding prophylaxis in the outpatient setting; this could permit reducing immunosuppression and decreasing the risk of treatment related infections. Two ongoing prospective clinical trials of emicizumab will help clarify the safety and efficacy in AHA.