Acquired hemophilia A: an updated narrative review

Acquired hemophilia A (AHA) is a rare autoimmune bleeding disorder caused by neutralizing autoantibodies against coagulation factor VIII (FVIII). It usually develops in older adults or during the postpartum period and often presents with new extensive subcutaneous, soft-tissue, muscular, mucosal, or internal bleeding in a person without a previous bleeding history. Diagnostic delay and treatment-related infection remain important causes of avoidable morbidity and mortality. This narrative review integrates international recommendations, registry data, prospective studies, and contemporary real-world evidence published through June 2026. A structured diagnostic pathway begins with recognition of an isolated prolonged activated partial thromboplastin time, exclusion of anticoagulant and pre-analytical effects, an immediate and incubated mixing study, measurement of FVIII activity, and confirmation of a FVIII inhibitor. Acute clinically significant bleeding requires prompt treatment with recombinant activated factor VII, activated prothrombin complex concentrate, or recombinant porcine FVIII; drug selection should reflect bleeding site, thrombosis risk, access, and monitoring capacity. Emicizumab, a subcutaneous bispecific FVIIIa-mimetic antibody, has emerged as effective bleed-prevention therapy while inhibitor eradication is pending. Prospective and real-world studies show substantial reductions in recurrent bleeding and may permit de-escalation or temporary postponement of intensive immunosuppression in selected frail patients. Nevertheless, emicizumab is not an acute rescue agent and does not eradicate the inhibitor. Immunosuppressive therapy therefore remains necessary for immunological remission in most patients, but its intensity should be individualized according to FVIII activity, inhibitor titer, frailty, infection, malignancy, and competing treatment risks. Laboratory monitoring during emicizumab exposure requires assay-specific planning. Modern AHA care should integrate rapid hemostatic control, early bleed prevention, and risk-adapted inhibitor eradication rather than applying a uniform treatment sequence. Clear laboratory communication, explicit definitions of remission, and coordinated follow-up at an experienced hemophilia center are essential to reduce both bleeding-related and treatment-related harm.