MTHFR and inherited thrombophilia: Hereditary thrombophilia is commonly caused by mutations in genes such as antithrombin (AT), protein C (PC), protein S (PS), coagulation factor V Leiden (FVL), plasminogen activator inhibitor-1 (PAI-1), and methylenetetrahydrofolate reductase (MTHFR), leading to loss of protein anticoagulant function or enhancement of procoagulant function, ultimately resulting in thromboembolism.