Severe Acquired Factor VIII Deficiency With Concomitant Lupus Anticoagulant: A Case Report.

Acquired hemophilia A (AHA) is a rare autoimmune bleeding disorder caused by autoantibodies against factor VIII (F VIII). The coexistence of AHA with lupus anticoagulant (LAC) is incredibly uncommon and presents a significant diagnostic challenge, as both conditions prolong activated partial thromboplastin time (aPTT) and demonstrate incomplete correction on mixing studies. We report a case of a 79-year-old man with no prior bleeding history who presented with severe anemia and a retroperitoneal hematoma following a fall. Laboratory evaluation revealed markedly prolonged aPTT, severely reduced F VIII activity (<7%), and an exceptionally elevated inhibitor titer (1084 Bethesda units), consistent with AHA. Concurrently, anticoagulant testing was done with a positive LAC presence. Extensive workup failed to identify an underlying etiology. The patient was subsequently treated with rituximab and corticosteroids, resulting in a gradual decline in aPTT and inhibitor titers with clinical improvement. This case highlights the importance of comprehensive coagulation testing in patients with unexplained bleeding and prolonged aPTT, as the coexistence of prothrombotic and hemorrhagic conditions can obscure diagnosis and delay appropriate management.