Table 4.

Hereditable thrombophilias

Thrombophilia	Mechanism causing hypercoagulability
Methylene tetrahydrofolate reductase mutation	Causes an increase in homocysteine, an amino acid intermediate in the metabolism of methionine which is linked to thrombosis
Protein C and S deficiency	Protein S is a cofactor for protein C, which is a proteolysis enzyme of factor Va and VIIIa
Antithrombin III deficiency	Antithrombin III is a protease for most clotting factors
Factor V Leiden mutation	The mutation results in an increase in the function of factor V, causing protein C to function improperly
G20210A mutation	Mutation in the prothrombin gene resulting in elevated plasma prothrombin

Note: Both the mutation or deficiency and the mechanism causing hypercoagulability are listed here for the most commonly tested hereditable thrombophilias.