Acquired circulating anticoagulants.

Acquired inhibitors of blood coagulation, which are pathologic circulating substances that directly inhibit clotting factors or their reactions, most commonly occur in patients with hereditary bleeding disorders. This article contains a discussion of acquired circulating anticoagulants that arise de novo in patients with previously normal hemostatic mechanisms. Pathogenesis and management are also discussed. Treatment of these patients poses a challenge for the hematologist because, unlike hereditary hemophiliacs who have learned to adjust their lifestyle, the acquired hemophiliac is unprepared for hemorrhagic episodes.