Thrombin generation and formation of thrombin-antithrombin III complexes in congenital antithrombin III deficiency

Two families with quantitative congenital AT III deficiency and a high incidence of thromboembolism are reported. In two unrelated patients (one from each family) thrombin generation in whole blood occured more rapidly than in the control, as demonstrated by the kinetics of prothrombin consumption, AT III disappearance and thrombin-antithrombin III complexes formation. Similar results were obtained in plasma and can be experimentally reproduced with a plasma depleted of AT III by immunoadsorption using a rabbit anti-AT III antiserum. The addition of purified AT III in vitro leads to a complete correction of the abnormalities when the level of AT III is greater than 0.8 unit/ml.