Idiopathic Acquired Hemophilia A With High-Titer Factor VIII Inhibitor in an Elderly Patient: A Case Report.

Acquired hemophilia A is a rare autoimmune bleeding disorder caused by neutralizing autoantibodies against factor VIII. It typically affects older adults and may present with spontaneous mucocutaneous bleeding, extensive ecchymoses, soft-tissue hematomas, and isolated prolongation of the activated partial thromboplastin time. We report the case of an 84-year-old woman with hypertension, hyperlipidemia, and anxiety who presented with several weeks of spontaneous nontraumatic bruising, fatigue, and exertional dyspnea. Initial evaluation revealed severe normocytic anemia, isolated aPTT prolongation, lack of correction on a mixing study, factor VIII activity <5%, and a high-titer factor VIII inhibitor of 470 Bethesda Units. Lupus anticoagulant testing was initially positive, while anticardiolipin and anti-β2-glycoprotein I antibodies were negative. The patient developed a right upper extremity hematoma and required a packed red blood cell transfusion. Immunosuppressive therapy with high-dose prednisone and weekly rituximab was initiated, with subsequent clinical improvement, normalization of aPTT, recovery of factor VIII activity, and disappearance of the inhibitor during follow-up. This case highlights the importance of considering acquired hemophilia A in elderly patients with spontaneous bleeding and isolated aPTT prolongation, even in the presence of transient lupus anticoagulant positivity.