The risk of recurrent venous thromboembolism among heterozygous carriers of the G20210A prothrombin gene mutation

The G20210A mutation in the prothrombin gene is associated with an increase d risk of a first venous thromboembolic episode; few data are available abo ut the long-term risk for recurrent venous thromboembolism and it is not kn own whether or not carriers of the mutation should be recommended lifelong anticoagulant treatment after the first thrombosis. We investigated 624 pat ients, referred for previous objectively documented deep venous thrombosis of the legs or pulmonary embolism, to determine the risk of recurrent throm boembolism in heterozygous carriers of the G20210A mutation in the prothrom bin gene after the first episode of venous thromboembolism. After exclusion of other inherited (anti-thrombin, protein C, protein S deficiency and fac tor V Leiden) or acquired (antiphospholipid antibody syndrome) causes of th rombophilia, 52 heterozygous carriers of the prothrombin mutation were comp ared with 283 patients with normal genotype. The relative risk for recurren t venous thromboembolism was calculated between groups using a Cox's propor tional hazard model. The patients with the prothrombin mutation had a risk for spontaneous recurrent venous thrombo embolism similar to that of patien ts with normal genotype (hazard ratio 1.3; 95% CI, 0.7-2.3). The circumstan ces of the first event (spontaneous or secondary) did not produce any subst antial variation in the risk for recurrence. In conclusion, the carriers of the prothrombin mutation should be treated with oral anticoagulants after a first deep venous thrombosis for a similar length of time as patients wit h a normal genotype.