A blood clot (thrombus) normally forms to stop the bleeding when an artery or vein is damaged, such as when you experience a cut. Clots are formed by chemical reactions between specialized blood cells (platelets) and proteins in your blood (clotting factors). Anti-clotting factors prevent an excessive formation of blood clots.
Normally, factor V is a clotting protein. Anti-clotting proteins break up factor V, keeping it from forming clots when clotting isn't needed.
Factor V Leiden makes it harder for anti-clotting proteins to break up factor V. This keeps factor V in the blood longer and increases the chance of clotting.
If you have factor V Leiden, you inherited either one copy (heterozygous) or, rarely, two copies (homozygous) of the defective gene. Inheriting one copy slightly increases your risk of developing blood clots. Inheriting two copies — one from each parent — significantly increases your risk of developing blood clots.
July 14, 2015
- Bauer KA. Management of inherited thrombophilia. http://www.uptodate.com/home. Accessed June 6, 2015.
- Cronenwett JL, et al. Hypercoagulable states. In: Rutherford's Vascular Surgery. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2014. http://www.clinicalkey.com. Accessed June 6, 2015.
- Kujovich JL. Factor V Leiden thrombophilia. Genetics in Medicine. 2011;13:1.
- AskMayoExpert. Factor V Leiden (FVL). Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2014.
- Bauer KA. Factor V Leiden and activated protein C resistance: Clinical manifestations and diagnosis. http://www.uptodate.com/home. Accessed June 6, 2015.
- Deep vein thrombosis. Merck Manual Professional Version. http://www.merckmanuals.com/professional/cardiovascular-disorders/peripheral-venous-disorders/deep-venous-thrombosis-dvt. Accessed June 6, 2015.
- Superficial venous thromobosis. Merck Manual Professional Version. http://www.merckmanuals.com/professional/cardiovascular-disorders/peripheral-venous-disorders/superficial-venous-thrombosis. Accessed June 6, 2015.
- What is pulmonary embolism? National Heart, Lung and Blood Institute. http://www.nhlbi.nih.gov/health/health-topics/topics/pe/signs. Accessed June 6, 2015.
- Bauer KA. Screening for inherited thrombophilia in asymptomatic individuals. http://www.uptodate.com/home. Accessed June 6, 2015.
- Lockwood CJ, et al. Inherited thrombophilias in pregnancy. http://www.uptodate.com/home. Accessed June 6, 2015.
- Cronenwett JL, et al. Acute deep venous thrombosis. In: Rutherford's Vascular Surgery. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2014. http://www.clinicalkey.com. Accessed June 6, 2015.
- Bauer KA, et al. Evaluating patients with established venous thromboembolism for acquired and inherited risk factors. http://www.uptodate.com/home. Accessed June 6, 2015.
- Raffini L. Screening for inherited thrombophilia in children. http://www.uptodate.com/home. Accessed June 6, 2015.
- Pulmonary embolism. Merck Manual Professional Version. http://www.merckmanuals.com/professional/pulmonary-disorders/pulmonary-embolism-pe/pulmonary-embolism-pe. Accessed June 6, 2015.
- Your guide to preventing and treating blood clots. Agency for Healthcare Research & Quality. http://www.ahrq.gov/patients-consumers/prevention/disease/bloodclots.html#preventing. Accessed June 6, 2015.
- Litin SC (expert opinion). Mayo Clinic, Rochester, Minn. June 16, 2015.
- Gómez-Outes A, et al. Dabigatran, Rivaroxaban, or Apixaban versus Warfarin in patients with nonvalvular atrial fibrillation: A systematic review and meta-analysis of subgroups. Thrombosis. 013; 2013: 640723. http://www.hindawi.com/journals/thrombosis/2013/640723/. Accessed June 16, 2015.
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