Acquired Circulating Anticoagulants in Hemophilia A

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Abstract
Factor VIII inhibitor was found in 16 of 77 patients (21 per cent) with severe hemophilia A. In 12 cases with marked inhibition, this became manifest after as few as 20, but no more than 90, accumulated days of exposure to transfusions, and usually before 10 years of age. Four to five days after antigenic stimulation from the infusion of factor VIII, the inhibitor level rose sharply, reached a peak at 10 to 14 days and then declined slowly. Peak inhibitor levels varied greatly in individual patients. On the basis of a patient's inhibitor level, the quantity of factor VIII needed to neutralize his inhibitor could be calculated. Thus, newer and more potent preparations could be rationally used. Eight episodes of life-threatening, enclosed soft-tissue bleeding in these patients required management by exchange transfusion. Sensitive methods for measurements of serum levels of inhibitor are imperative for the management of patients with hemophilia.