A Swedish family with abnormal antithrombin III

An abnormal variant of antithrombin III is reported in a young male with deep vein thrombosis. The heparin cofactor, progressive thrombin inhibition, and factor Xa inactivation are decreased. The abnormality seems to be a mutation which is transmitted in an autosomaldominant way. The half-life and fractional catabolic rate of 125I antithrombin III concentrate is the same in this patient as in patients with the classic type of antithrombin III deficiency and in a control.