F5

About F5

F5 on chromosome 1q24.2 encodes coagulation factor V, a cofactor that, once activated, greatly accelerates the conversion of prothrombin to thrombin. Activated factor V is normally switched off when activated protein C cleaves it. The Factor V Leiden variant, named after the Dutch city where it was identified in 1994, changes the amino acid at one of these cleavage sites, making factor V resistant to inactivation by activated protein C. This leads to a hypercoagulable state and an increased tendency to form venous blood clots, such as deep vein thrombosis and pulmonary embolism. It is the most common inherited risk factor for venous thrombosis in people of European ancestry, while it is rare in African and East Asian populations. Most people with one copy never develop a clot, and the risk is influenced by other factors such as pregnancy, estrogen containing medications, surgery, and immobility.