Activated Protein C Resistance and Factor V Leiden: A Review (Report‪)‬

Factor V Leiden (FVL) describes a G1691A nucleotide transition resulting in an R506Q amino acid missense mutation. Early papers showed that the resulting factor V protein was resistant to proteolysis by activated protein C (APC), and it is now recognized that FVL accounts for 90% to 95% of cases of APC resistance. Factor V resistance to APC has an incidence of 4.8% in the general population and is the most common cause of inherited thrombosis, accounting for 40% to 50% of cases. (1) In contrast, the second most common genetic mutation that results in thrombosis, the G20210A prothrombin mutation, occurs in 2.7% of normal patients, with the frequency increasing to 7.1% to 16% in affected patients. (2) FVL mutation is more frequently found in cases of venous thrombosis than are protein C or S deficiency, the prothrombin G20210A mutation, and antithrombin deficiency combined. In contrast, the FVL mutation is extremely uncommon in people of African or Asian descent, and was thought to have emerged 30 000 years ago, with divergence of Caucasian, Asian, and African populations. (3) EPIDEMIOLOGY AND DISEASE ASSOCIATION