Critical limb ischemia leading to amputation as a presentation of acquired hemophilia A with congenital factor XII deficiency: a case report.

introduction and importanceAcquired Hemophilia A (AHA) is a rare autoimmune bleeding disorder caused by autoantibodies against factor VIII. Diagnosis is often delayed when confounding factors coexist. PRESENTATION OF CASE: We report a 70-year-old male with peripheral arterial disease presenting with critical limb ischemia, severe anemia, and prolonged APTT. Investigations revealed factor VIII inhibitor, concomitant factor XII deficiency, and lupus anticoagulant positivity. CLINICAL DISCUSSION: The combination of FXII deficiency and lupus anticoagulant created significant diagnostic confusion, as both are associated with prolonged APTT but not with bleeding. This overlap risked masking the hemorrhagic tendency of AHA. Management required bypassing agents, surgery, immunosuppressive therapy with corticosteroids and rituximab, and multidisciplinary care.

conclusionThis case highlights the importance of considering acquired hemophilia A in unexplained bleeding with prolonged APTT, especially when coexisting conditions such as FXII deficiency and lupus anticoagulant may obscure diagnosis.