A NEW ASYMPTOMATIC TYPE III VARIANT OF ANTITHROMBIN III WITH DECREASE HEPARIN COFACTOR ACTIVITY : AT III AMIENS
A qualitative abnormality of AT III suggested by the discrepancy between a normal level of AT III antigen (0,33 g/1) and a decreased heparin cofactor activity (60 % of normal) was discovered in a 37 years old woman during a routine laboratory examination for oral contraceptive. The propositus was asymptomatic as she did not developpe any thrombo-embolic disease during three previous pregnancies. There was no familial history of thrombo-embolism. The AT III level measured by radial immuno-diffusion was within the normal range. The progressive anti factor lia and anti factor Xa activities (chromogenic substrates CBS 3 447 and CBS 3 139) were normal (92 % and 100 %). Plasma and serum crossed immunoelectrophoresis (CIE) showed a normal pattern. In the presence of heparin, anti factor Xa and anti factor Xa activities were decreased (60 % and 45 %); Plasma and serum crossed immunoelectrophoresis showed an abnormal slow moving peak exhibiting the inhability of the molecule to bind completely to heparin. CIE with various other glycosaminoglycans are on experiments.Familial study revealed that the daughter of the propositus was carrying the same molecular abnormality.We conclude that AT III Amiens is an hereditary type III variant.