F5 and Rare hereditary thrombophilia: The heritable thrombophilia includes a deficiency in the natural anticoagulants, including anti-thrombin (AT), protein C (PC), and protein S (PS), and the presence of specific variants affecting coagulation factors, most commonly factor V Leiden (FVL; p.Arg506Gln), and prothrombin (PTH; G20210A) variants.