Pregnancy-Associated Acquired Hemophilia A (PA-AHA) Treated Successfully With the Factor-Mimetic Bispecific Antibody Emicizumab: A Case Report and Literature Review

Acquired hemophilia A (AHA) is a rare bleeding disorder characterized by spontaneous bleeding in individuals with no previous personal or family history of bleeding, caused by the development of autoantibodies against coagulation Factor VIII (FVIII). These autoantibodies may be associated with drugs, autoimmune disorders, malignancies, and pregnancy. Pregnancy-associated AHA (PA-AHA) is a very rare condition, accounting for approximately 1%-5% of all AHA cases. Emicizumab, a bispecific FVIII-mimetic monoclonal antibody, was originally approved for Congenital Hemophilia A (with or without FVIII inhibitors) and has since gained widespread recognition and clinical utility in the management of AHA as well. We report a case of PA-AHA that was successfully managed with emicizumab. A 46-year-old woman was admitted with vaginal bleeding and extensive ecchymoses. The patient's obstetric history was notable for a twin gestation achieved through in vitro fertilization (IVF) using donor oocytes. The patient reported recurrent ecchymoses and menorrhagia beginning in the postpartum period. Laboratory examination revealed severe anemia with normal platelet counts and prothrombin time (PT), but a markedly prolonged activated partial thromboplastin time (aPTT) of 94.5 s. Immunological and virology testing, as well as cancer biomarkers, were negative. Initially, the patient received bypassing hemostatic therapy with recombinant activated Factor VII (rFVIIa), along with intensive immunosuppressive therapy (IST) consisting of corticosteroids, rituximab, and cyclophosphamide, in accordance with current international recommendations. However, no clinical response was observed. Treatment with emicizumab was subsequently initiated according to the proposed dosing schedule. Within 2 days, all bleeding manifestations resolved rapidly. Notably, FVIII activity, measured using a chromogenic assay, remained markedly reduced. After 566 days of follow-up, FVIII activity spontaneously normalized, allowing discontinuation of emicizumab. No further bleeding episodes were observed. Although emicizumab is increasingly incorporated into the management of AHA, clinical experience in PA-AHA remains limited. The present case adds to the existing literature by supporting the safety and efficacy of emicizumab in PA-AHA, highlighting its role as an effective hemostatic bridge to remission in complex clinical settings.