A macroglobulin with inhibitory activity against coagulation factor VIII.

H EMOSTATIC DISORDERS with a varying incidence of bleeding, are common in the dysproteinemias, and are characteristic of the macroglobulinemia of \\Taldenstr#{246}m These abnormalities are most frequently attributed to abnormal platelet function,1 and depression of specific clotting factors appears to be a rare occurrence. Nilehn2 includes four instances of antihemophilic globulin ( factor VIII ) deficiency in a survey of macroglobulinemia among other disorders, but does not elaborate on the mechanism. In contrast, other authors3’4 have found high levels of factor VIII in the dysproteinemias, including macroglobulinemia. The present report is concerned with acquired deficiency of factor VIII occurring in a patient with macroglobulinemia, in whom clinical and laboratory studies indicate that the macroglobulin behaved as an inhibitor of this factor.