Coagulation is a complex process to form clots of platelets and fibrin to stop bleeding.

After damage of a blood vessel a cascade of signals is initiated (extrinsic), starting with Factor (F) VII to activate FIX and FX and its cofactor FVa to release thrombin from prothrombin (FII), which allows to convert fibrinogen to fibrin and to crosslink it (through FXIII), but also activates FV, FVIII and their inhibitor protein C (compressed summary).

Increased risk of bleeding and increased clotting (thrombosis) are well-known disorders of coagulation. There are several mutations in these genes known, having an influence on the coagulation. Most prominent is the FV variant R506Q, causing APC resistance and increasing the risk for thrombosis. Also well-known is the prothrombin (F2) G20210A mutation, increasing the risk for blood clots in the deep veins.