Antithrombin III deficiency in a Romanian family. Pathogenic role of concomitantly increased plasma level of clotting factors VII and X.

Antithrombin III deficiency in a Romanian family is presented. The propositus, a 27 year-old man, had a history of recurrent venous thrombosis and was found to present a plasma antithrombin III level of only 50% of the normal values. His mother and two of his five children had low antithrombin III levels but no episodes of venous thrombosis. In opposition to his family members, the propositus presented overweight, slight hypertriglyceridemia and displayed a high level of clotting factors VII and X. The findings suggest that development of thromboembolic disease in a subject with familial antithrombin III deficiency is enhanced by additional factors, for example by an increased plasma level of vitamin K-dependent clotting factors.