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F5 gene

coagulation factor V

Normal Function

The F5 gene provides instructions for making a protein called coagulation factor V. Coagulation factors are a group of related proteins that make up the coagulation system, a series of chemical reactions that form blood clots. After an injury, clots seal off blood vessels to stop bleeding and trigger blood vessel repair.

The factor V protein is made primarily by cells in the liver. The protein circulates in the bloodstream in an inactive form until the coagulation system is activated by an injury that damages blood vessels. When coagulation factor V is activated, it interacts with coagulation factor X. The active forms of these two coagulation factors (written as factor Va and factor Xa, respectively) form a complex that converts an important coagulation protein called prothrombin to its active form, thrombin. Thrombin then converts a protein called fibrinogen into fibrin, which is the material that forms the clot.

Coagulation factor V has another role in regulating the coagulation system through its interaction with activated protein C (APC). APC normally inactivates coagulation factor V by cutting (cleaving) it at specific sites. This inactivation slows down the clotting process and prevents clots from growing too large. When coagulation factor V is cleaved at a particular site (protein position 506), it can work with APC to inactivate factor VIIIa, which is another protein that is essential for normal blood clotting.

Health Conditions Related to Genetic Changes

Factor V deficiency

At least 100 variants (also called mutations) in the F5 gene have been found to cause a rare bleeding disorder called factor V deficiency. These variants prevent the production of functional coagulation factor V or significantly reduce the amount of the protein in the bloodstream. People with this condition typically have less than 10 percent of normal levels of coagulation factor V in their blood; the most severely affected individuals have less than 1 percent. A reduced amount of functional factor V prevents blood from clotting normally, causing episodes of abnormal bleeding that can be severe. Factor V deficiency results from variants in both copies of the F5 gene, although some people with a variant in a single copy of the gene have mild bleeding problems.

More About This Health Condition

Factor V Leiden thrombophilia

Factor V Leiden is the name of a specific variant in the F5 gene. This variant changes a single protein building block (amino acid) in the factor V protein. Specifically, it replaces the amino acid arginine with the amino acid glutamine at protein position 506 (written as Arg506Gln or R506Q). Because position 506 is one of the sites where APC normally cleaves coagulation factor V, the factor V Leiden variant slows the rate at which APC inactivates this factor. As a result, both the activated form of coagulation factor V and coagulation factor VIIIa persist longer in circulation, increasing the risk of developing an abnormal blood clot. This tendency to form abnormal clots that can block blood vessels is known as thrombophilia.

The presence of the factor V Leiden variant in one or both copies of the F5 gene can cause thrombophilia; two copies of the variant lead to a higher risk of developing abnormal blood clots than a single copy of the variant.

More About This Health Condition

Other disorders

Some people have the factor V Leiden variant (Arg506Gln) in one copy of the F5 gene and a variant associated with factor V deficiency in the other copy of the gene in each cell. The factor V Leiden variant results in the production of an abnormal coagulation factor V protein that is resistant to inactivation by APC, while the other variant prevents the production of any coagulation factor V protein. This combination of variants is associated with an increased risk of abnormal blood clots similar to the risk associated with having two copies of the factor V Leiden variant. This rare condition is known as pseudohomozygous APC resistance or pseudohomozygous factor V Leiden.

The factor V Leiden variant is involved in some cases of a condition known as Budd-Chiari syndrome. This condition is characterized by a blockage of blood flow from the liver, which can be caused by a blood clot. People with thrombophilia, including that caused by the factor V Leiden variant, have an increased risk of developing Budd-Chiari syndrome. Signs and symptoms of the syndrome include pain in the abdomen, an abnormally large liver (hepatomegaly), and accumulation of fluid in the lining of the abdomen (ascites).

Other Names for This Gene

  • blood coagulation factor V
  • coagulation factor V (proaccelerin, labile factor)
  • factor V

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases


  • Asselta R, Peyvandi F. Factor V deficiency. Semin Thromb Hemost. 2009 Jun;35(4):382-9. doi: 10.1055/s-0029-1225760. Epub 2009 Jul 13. Citation on PubMed
  • Asselta R, Tenchini ML, Duga S. Inherited defects of coagulation factor V: the hemorrhagic side. J Thromb Haemost. 2006 Jan;4(1):26-34. doi: 10.1111/j.1538-7836.2005.01590.x. Citation on PubMed
  • Brugge JM, Simioni P, Bernardi F, Tormene D, Lunghi B, Tans G, Pagnan A, Rosing J, Castoldi E. Expression of the normal factor V allele modulates the APC resistance phenotype in heterozygous carriers of the factor V Leiden mutation. J Thromb Haemost. 2005 Dec;3(12):2695-702. doi: 10.1111/j.1538-7836.2005.01634.x. Citation on PubMed
  • Castoldi E, Rosing J. Factor V Leiden: a disorder of factor V anticoagulant function. Curr Opin Hematol. 2004 May;11(3):176-81. doi: 10.1097/01.moh.0000130315.41033.32. Citation on PubMed
  • Colak Y, Karasu Z, Oruc N, Can C, Balym Z, Akarca U, Gunsar F, Ersoz G, Tokat Y, Batur Y. Hyperhomocysteinaemia and factor V Leiden mutation are associated with Budd-Chiari syndrome. Eur J Gastroenterol Hepatol. 2006 Aug;18(8):917-20. doi: 10.1097/00042737-200608000-00019. Citation on PubMed
  • Cutler JA, Patel R, Rangarajan S, Tait RC, Mitchell MJ. Molecular characterization of 11 novel mutations in patients with heterozygous and homozygous FV deficiency. Haemophilia. 2010 Nov;16(6):937-42. doi: 10.1111/j.1365-2516.2010.02330.x. Citation on PubMed
  • Duga S, Asselta R, Tenchini ML. Coagulation factor V. Int J Biochem Cell Biol. 2004 Aug;36(8):1393-9. doi: 10.1016/j.biocel.2003.08.002. Citation on PubMed
  • Grody WW, Griffin JH, Taylor AK, Korf BR, Heit JA; ACMG Factor V. Leiden Working Group. American College of Medical Genetics consensus statement on factor V Leiden mutation testing. Genet Med. 2001 Mar-Apr;3(2):139-48. doi: 10.1097/00125817-200103000-00009. No abstract available. Erratum In: Genet Med. 2021 Dec;23(12):2463. doi: 10.1038/s41436-021-01108-x. Citation on PubMed or Free article on PubMed Central
  • Janssen HL, Meinardi JR, Vleggaar FP, van Uum SH, Haagsma EB, van Der Meer FJ, van Hattum J, Chamuleau RA, Adang RP, Vandenbroucke JP, van Hoek B, Rosendaal FR. Factor V Leiden mutation, prothrombin gene mutation, and deficiencies in coagulation inhibitors associated with Budd-Chiari syndrome and portal vein thrombosis: results of a case-control study. Blood. 2000 Oct 1;96(7):2364-8. Citation on PubMed
  • Lak M, Sharifian R, Peyvandi F, Mannucci PM. Symptoms of inherited factor V deficiency in 35 Iranian patients. Br J Haematol. 1998 Dec;103(4):1067-9. doi: 10.1046/j.1365-2141.1998.01077.x. Citation on PubMed
  • Mann KG, Kalafatis M. Factor V: a combination of Dr Jekyll and Mr Hyde. Blood. 2003 Jan 1;101(1):20-30. doi: 10.1182/blood-2002-01-0290. Epub 2002 Aug 8. No abstract available. Citation on PubMed
  • Nicolaes GA, Dahlback B. Factor V and thrombotic disease: description of a janus-faced protein. Arterioscler Thromb Vasc Biol. 2002 Apr 1;22(4):530-8. doi: 10.1161/01.atv.0000012665.51263.b7. Citation on PubMed
  • Ornstein DL, Cushman M. Cardiology patient page. Factor V Leiden. Circulation. 2003 Apr 22;107(15):e94-7. doi: 10.1161/01.CIR.0000068167.08920.F1. No abstract available. Citation on PubMed
  • Rosendorff A, Dorfman DM. Activated protein C resistance and factor V Leiden: a review. Arch Pathol Lab Med. 2007 Jun;131(6):866-71. doi: 10.5858/2007-131-866-APCRAF. Citation on PubMed
  • Segers K, Dahlback B, Nicolaes GA. Coagulation factor V and thrombophilia: background and mechanisms. Thromb Haemost. 2007 Sep;98(3):530-42. Citation on PubMed
  • Vos HL. Inherited defects of coagulation Factor V: the thrombotic side. J Thromb Haemost. 2006 Jan;4(1):35-40. doi: 10.1111/j.1538-7836.2005.01572.x. Epub 2005 Oct 25. Citation on PubMed

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.