Factor V Leiden Mutation Causing Thrombophilia

It has autosomal dominant inheritance and is the most common cause of inherited thrombophilia. FVL is the most prevalent thrombotic risk factor known in the Caucasian population (around 5%). [1] Heterozygotes have a three to five times increased risk of thrombosis. Homozygotes are much less common but have a much higher thrombotic risk, around eight times increased risk. It leads to a hypercoagulable state. Heterozygous FVL mutation and the G20210A mutation in the prothrombin gene are the most frequent clotting abnormalities associated with venous thromboembolism (VTE). The two mutations may co-exist. An individual may be heterozygote or homozygote for the FVL mutation. It is difficult to estimate the increased risk of thrombosis in given individuals, particularly heterozygotes, due to the variable penetrance of the thrombotic tendency (interaction with rest of genotype) and variation in other risk factors. Heterozygous carriers have a 4to 8-fold increased risk of VTE and homozygotes have an 80fold increased risk. [1] The risk of VTE of a FVL mutation is considerably lower than a deficiency of protein C, protein S, or antithrombin III. [2]