[Interaction of estrogens and genetic risk factors for thrombosis]

Deep venous thrombosis (DVT) is associated with a genetic risk factor in about half of all cases. Antithrombin, protein C or protein S deficiencies account for 5 to 10 per cent of hereditary thrombophilia whereas the Arg 506 Gln factor V mutation is found in 20 to 30 per cent of DVTs and the G20210A factor II gene mutation in 5 to 10 per cent of them. The risk for DVT is increased three- to fourfold in women using oral contraceptives (OC); it is also increased during menopause hormonotherapy. Oestrogens modify the haemostatic balance, inferring a role in the thrombotic risk. The only thrombophilic factor which in association with OC was demonstrated to multiply the risk is the factor V Arg 506 Gln mutation, with a relative risk around 30. This observation reinforces the hypothesis that venous thrombosis is a multifactorial disease.