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| Factor V Leiden Thrombophilia is the most common inherited disorder of blood clotting. It is the result of a specific mutation in the gene for factor V which leads to increased risk for clots in the large veins of the legs (deep venous thrombosis), or clots that travel though the bloodstream and embed in the lungs (pulmonary embolism). It is inherited in an autosomal dominant manner. If a person inherits one copy of the mutated gene, he or she has a 2 to 8 times risk (2 to 8 in 1,000) for developing clots. If a person inherits two copies of the factor V Leiden mutation, the risk increases up to 80 times (80 in 1,000). It is estimated that three to eight per cent of the Caucasian population and 1.2 percent of the African-American population in the U.S. carry one copy of the gene and about 1 in 1000 Caucasians have two copies of the gene.
Testing: DNA analysis of the Factor V gene.
Who should be tested?
- History of venous thrombosis or pulmonary embolism, especially recurrent thrombosisHistory of transient ischemic attacks or premature strokeFamily history of thrombosisFactor V mutation in a relativeIf there is a personal or family history of clots, individuals should be tested prior to major surgery, pregnancy, postpartum, oral contraceptives or hormone replacement therapy
- Previous finding of activated protein C analysis by laboratory analysis
Pregnancy: It is thought that Factor V Leiden increases the risk for recurrent fetal loss and has been associated with severe pre-eclampsia, unexplained intrauterine growth retardation, placental abruption, and stillbirth as well as maternal clotting during labor and in the postpartum period.
Contributing factors that increase the risk of thrombosis: obesity, smoking, oral contraceptives, surgery, trauma, and high blood pressure.
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Factor V Leiden Thrombophilia
J. Kujovich and S. Goodnight, Gene Reviews, February 12, 2007
 [for Professionals mainly]
" ... Factor V. Leiden thrombophilia is characterized by a poor anticoagulant response to activated protein C (APC), and an increased risk of venous thromboembolish ... suspected in individuals with a history of venous thrombosis ... women who use oral contraceptives... the risk of thrombosis increases to more that 30-fold in heterozygotes and to several hundred fold in homozygotes ... factor V Leiden were found in 21-52% of pediatric patients with venous thromboembolism ... not considered a major risk factor for arterial thrombosis (but) ... may occur in the fetus ... more pregnancy losses ...prophylactic pregnancy ... no consensus ...
Factor V. Leiden APC Resistance
Johns Hopkins University, February 9, 2007
[for Professionals mainly]
Omim comprehensive clinical and genetic review - 1998.
Consensus Statement on Factor V Leiden Mutation Testing
W. Grody, MD et al. (ACMG Factor V Leiden Working Group), American College of Medical Genetics, 2006
[for Professionals mainly]
Which methodology should be used: Factor V Leiden DNA testing or functional activated protein C (APC) resistance testing ... Who should be tested ... individuals with environmental risk factors ... other heritable thrombophilic risk factors ... appropriate pre- and postanalytic procedures ...
Factor V Leiden / Thrombophilia Support Page
Deborah Okner Smith, July 10, 2007
[Support Group]
... most common hereditary blood coagualtion disorder in the United States ... 5% of the Caucasian population and 1.2% of the African American population ... complications ... Venous Thrombosis ... Pulmonary Embolism (PE) ... Arterial clots (stroke, heart attack) ... Preeclampsia and/or eclampsia (toxemia while pregnant) ...
Factor V Leiden
Reviewed by Dr. Patrick Davey et al, NetDoctor.co.uk., February 6, 2005
[Support Group]
Blood Disorder (Factor V)
UAB Health System (Dear Doctor Column, October 21, 2002)
Venous Thrombosis and the Factor V (Leiden) Mutation
Annette K. Taylor, PhD Genetic Drift Newsletter (Vol. 14: Spring, 1997)
Factor V Leiden thrombophilia
Genetics Home Reference, May 2005
Patient Resources (Factor V Leiden)
University of Illinois - Urbana/Champaign, Carle Cancer Center
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Last Updated: 2007/08/20
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