Acquired hemophilia A is a potentially severe bleeding disorder caused by antibodies against the patient's own factor VIII. Acquired hemophilia A is rare. It is most commonly diagnosed in older individuals; about one-half of cases of acquired hemophilia are associated with underlying conditions, including autoimmune disease, cancer, and pregnancy. The diagnosis of acquired hemophilia A can be suspect with an isolated activated partial thromboplastin time elevation, and confirmed with demonstration of reduced factor VIII activity and the presence of a specific factor VIII inhibitor. Treatment of acquired hemophilia A involves control of bleeding, and eradication of the inhibitor.