Key polymorphisms, such as Factor V Leiden (FVL), prothrombin G20210A mutation (FII), methylenetetrahydrofolate reductase (MTHFR C677T and MTHFR A1298C) polymorphisms, and plasminogen activator inhibitor-1 (PAI-1), play a crucial role in thrombophilia, when present alone or in combination. Here, SERPINE1 is linked to Rare hereditary thrombophilia.