[G20210A transition in the prothrombin gene and venous thromboembolic disease]

Genetic predisposition to venous thrombosis can be due to coagulation inhibitor deficiencies (antithrombin, protein C or protein S) or to activated protein C resistance resulting from factor V Leiden mutation (FV Leiden). Poort et al. recently identified a new polymorphism in the 3'-untranslated region of the prothrombin gene, the G20210A transition (FII G20210A), which was found to be associated with an increased risk of venous thrombosis.

The prevalence of the A allele is approximately 1 to 4% in the general population, and 5 to 7% in patients with venous thrombosis. Heterozygous carriers have a three to five times increased risk of thrombosis. The diagnosis is based on a polymerase chain reaction technique and restriction enzyme digestion from genomic DNA. Recent studies aim to determine the relative risk of thrombosis and the clinical features which are associated with the mutation (age of first thrombosis, recurrence). The thrombotic risk seems to be higher when FII G20210A transition is associated with the FV Leiden mutation.

The presence of heterozygous FII G20210A transition does not modify the management of acute thrombotic events but can lead to an increase in the duration of the anticoagulant treatment. When such a genetic abnormality is identified, thorough information of the patient is needed, including on the prophylactic heparin in high-risk situations and caution on the prescription of oral contraceptives containing estrogens.