Factor Five Leiden F V (F V Arg506Gln G>A)

Factor V (Leiden) of the blood coagulation system is the major plasmatic cofactor in the conversion of prothrombin to thrombin. Changes in the gene lead to the acquisition of resistance to the action of activated protein C, an increased risk of thrombosis (Leyden mutation). It has a prognostic value in hormone replacement therapy, oral contraceptives.

Possible genotypes:

 • G/G – "normal" blood clotting

 • G/A – increased blood clotting

 • A/A – increased blood clotting