MTHFR and Rare hereditary thrombophilia: Currently, seven variants in five genes are routinely genotyped as genetic risk factors of inherited thrombophilia: F5 c.1601G>A (factor V Leiden, FVL), F2 c.*97G>A (factor II G20210A or PTM, prothrombin mutation), two MTHFR (methylenetetrahydrofolate reductase) variants, two PAI-1 (plasminogen activator inhibitor 1) variants, and F13A1 (factor XIII) c.103G>T (FXIII, V35L) (3-9).