Hereditary antithrombin III deficiency and thromboembolic disease.

Two teenage brothers with recurrent thromboembolic disease were found to have antithrombin III deficiency. A family study spanning four generations revealed a total of 10 members with antithrombin III deficiency. Five of the 10 affected family members have had thrombotic problems. Antithrombin III deficiency was documented by coagulation assays measuring heparin cofactor, anti-Factor Xa, and progressive antithrombin activity; the level of antithrombin III antigenic material measured by immunoelectrophoresis was low in subjects with abnormal coagulation assays. The clinical features which may lead one to suspect the hereditary hypercoagulable condition of antithrombin III deficiency are reviewed.