Unexplained bleeding and a hidden inhibitor: A case of late-onset acquired hemophilia A

Abstract Background: Acquired hemophilia A (AHA) is a rare autoimmune bleeding disorder caused by autoantibodies against factor VIII. It primarily affects older adults and typically presents with spontaneous bleeding in patients without prior bleeding history. Early diagnosis is critical due to the high risk of severe hemorrhage and mortality.Case Presentation: A 69-year-old male with a history of hypertension, type 2 diabetes mellitus, stage 4 chronic kidney disease (CKD), and previous ischemic stroke presented with two weeks of progressive fatigue and abdominal pain. One week prior, he sustained a fall with minor head trauma for which he went to a local hospital and was found to have a small subdural hematoma. He was discharged after clinical stabilization without bleeding complications. Despite initial clinical stability, he developed worsening fatigue, abdominal pain, and extensive ecchymoses. No prior personal or family history of bleeding disorder. On this admission, he was severely anemic (Hb 2.8 g/dL) with worsening renal function and hyperkalemia requiring urgent Hemodialysis. CT imaging revealed a large left rectus sheath hematoma and evolving intramuscular hematomas. Coagulation studies showed isolated prolonged aPTT that failed to correct with mixing studies. Factor assays were delayed due to administration of fresh frozen plasma (FFP) for active bleeding from the dialysis catheter site and evolving hematomas. Subsequent testing revealed <1% Factor VIII activity and a high-titer of factor VIII inhibitor (69 BU), confirming AHA with no identifiable malignancy, lymphoproliferative or autoimmune disorder. The patient was treated initially with recombinant porcine Factor VIII (Obizur) without sustained response, then switched to recombinant activated Factor VII (NovoSeven) for hemostasis. Immunosuppressive therapy with prednisone and rituximab was initiated. Supportive care included blood transfusions, intravenous iron, erythropoiesis-stimulating agents (ESAs), and dialysis for CKD. Hemoglobin stabilized, and bleeding episodes ceased. The patient remained under close monitoring in the intensive unit due to the complexity of his comorbid conditions and immunosuppressive treatment.Discussion: This case highlights the diagnostic challenges of AHA, especially when urgent blood product transfusions and invasive procedures precede confirmatory testing. Persistent bleeding from vascular access sites should raise suspicion of acquired bleeding disorders. Prolonged aPTT uncorrected by mixing studies is a key diagnostic clue. Management requires acute bleeding control with bypassing agents and inhibitor eradication with immunosuppressive therapy. Early recognition and treatment reduce morbidity and mortality.Conclusion: AHA should be considered in elderly patients with unexplained bleeding and isolated prolonged aPTT, even following trauma. Increased awareness and timely intervention can significantly improve outcomes in this rare but potentially fatal disorder.