Factor V Leiden thrombophilia

What causes factor V Leiden thrombophilia?

Factor V Leiden thrombophilia is caused by a specific mutation in the F5 or Factor Vgene. F5 plays a critical role in the formation of blood clots in response to injury. Genes are our body’s instructions for making proteins. F5 instructs the body how to make a protein called coagulation factor V. Coagulation factor V is involved in a series of chemical reactions that hold blood clots together. A molecule called activated protein C (APC) prevents blood clots from growing too large by inactivating factor V. Factor V Leiden gene mutations cause factor V to be inactivated more slowly than normal. This leaves more time for blood clots to form.

Last updated on 05-01-20

How is factor V Leiden thrombophilia diagnosed?

The APC (activated protein C) resistance assay, a coagulation screening test, measures the anticoagulant response to APC. This screening test has a sensitivity and specificity for factor V Leiden approaching 100%. The sensitivity of a test is a measure of the test's ability to detect a positive result when someone has the condition, while the specificity is a measure of the test's ability to identify negative results.

Targeted mutation analysis (a type of DNA test) of the F5 gene for the Leiden mutation is considered definitive and has a mutation detection frequency of approximately 100%. This means that approximately all individuals who have the factor V Leiden mutation will be detected by this genetic test. It is generally recommended that individuals who test positive by another means should then have the DNA test both for confirmation and to distinguish heterozygotes (individuals with a mutation in one copy of the gene) from homozygotes (individuals with mutations in both copies of the gene).

Last updated on 05-01-20

How is factor V Leiden thrombophilia diagnosed?

A diagnosis of factor V Leiden thrombophilia may be considered in people with a notable personal or family history of venous thromboembolism (VTE), such as having a VTE at an atypically young age, in an unusual location, or having multiple VTEs. A doctor may confirm the diagnosis by ordering a genetic or APC resistance test. Alternatively, it is becoming more common for people to learn they have a factor V Leiden gene mutation from an advertised genetic test they purchased directly.

Last updated on 05-01-20

How is factor V Leiden inherited?

We all inherit two copies of the F5 (factor V) gene. We inherit one copy from our mother and the other from our father. As a result, our risk for having factor V Leiden thrombophilia depends on the genetic status of each of our parents.

Most people with factor V Leiden thrombophilia have one "normal" F5 gene and one with the factor V Leiden gene mutation. People with one copy of the mutation are called heterozygotes. Assuming this person and a person without the mutation have a child, this couple would have a 50%, or 1 in 2 chance of having a child with a single F5 mutation.

Factor V Leiden thrombophilia is a relatively common condition. In some families, both parents have the F5 mutation. In this scenario, each child of the couple would have a 25% or 1 in 4 chance of having two mutations, a 25% chance of having no mutation, and a 50% chance of having a one mutation.

People with two copies of the F5 mutation are said to be " homozygotes." They will always pass one copy of the mutated gene to their children. A child's risk for a second mutation will depend on whether or not his or her other parent has the F5 mutation.

Last updated on 05-01-20

How common is factor V Leiden thrombophilia?

The factor V Leiden mutation is the most common inherited risk factor for abnormal blood clotting in the United States. Factor V Leiden mutations are estimated to be carried by:

5% of Caucasians
2% of Hispanic Americans
1% Native Americans
1% African Americans
0.5% Asian Americans

In addition, up to 14% of people in populations from Greece, Sweden, and Lebanon are thought to carry factor V Leiden.

Having two factor V Leiden mutations is much rarer, affecting around 1 in 1,600 people.

Last updated on 05-01-20

How might factor V Leiden be treated?

Treatment of factor V Leiden thrombophilia varies depending on the patient's medical history and current circumstances.

People with factor V Leiden thrombophilia who've had a deep venous thrombosis (DVT) or pulmonary embolism (PE) are usually treated with blood thinners, or anticoagulants (such as heparin and warfarin). Anticoagulants are given for varying amounts of time depending on the person's situation. It is not usually recommended that people with factor V Leiden be treated lifelong with anticoagulants if they have had only one DVT or PE, unless they have additional blood clot risk factors.

People who have factor V Leiden but have never had a blood clot are not routinely treated with an anticoagulant. Instead, they are counseled about reducing or eliminating other factors that add to their risk for clots. They may require temporary treatment with an anticoagulant during periods of particularly high risk, such as major surgery.

Women with factor V Leiden thrombophilia most often have normal pregnancies. Treatment with an anticoagulant during pregnancy and/or following delivery is often not needed, but may be recommended depending on the woman's personal and family health history, method of delivery, and other risk factors.

Last updated on 05-01-20

Where To Start

American Heart Association

The American Heart Association has published an article for patients on factor V Leiden.

Last updated on 04-27-20

Name: National Blood Clot Alliance 8321 Old Courthouse Road Suite 255
Vienna, VA, 22182, United States
Phone: +1-703-935-8845 Toll Free: 1-877-466-2568 (877-4NO-CLOT) Email: info@stoptheclot.org Url: https://www.stoptheclot.org/
Name: Vascular Cures 274 Redwood Shores Parkway, #717
Redwood City, CA, 94065, United States
Phone: +1-650-368-6022 Email: info@vascularcures.org Url: https://vascularcures.org/
Name: Clot Connect UNC Hemophilia and Thrombosis Center 6340 Quadrangle Drive, Suite 50
Chapel Hill, NC, 27517, United States
Email: http://www.clotconnect.org/about-clot-connect/contact-u Url: http://www.clotconnect.org/
Kujovich JL. Factor V Leiden Thrombophilia GeneReviews. 2010; Reference Link

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