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Learning About Factor V Leiden Thrombophilia
What is factor V Leiden thrombophilia?
Factor V Leiden thrombophilia is an inherited disorder of blood clotting. Factor
V Leiden is the name of a specific mutation (genetic alteration) that results
in thrombophilia, or an increased tendency to form abnormal blood clots in blood
vessels. People who have the factor V Leiden mutation are at somewhat higher
than average risk for a type of clot that forms in large veins in the legs (deep
venous thrombosis, or DVT) or a clot that travels through the bloodstream and
lodges in the lungs (pulmonary embolism, or PE).
Factor V Leiden is the most common inherited form of thrombophilia. Between
3 and 8 percent of the Caucasian (white) U.S. and European populations carry
one copy of the factor V Leiden mutation, and about 1 in 5,000 people have two
copies of the mutation. The mutation is less common in other populations.
A mutation in the factor V gene (F5) increases the risk of developing factor
V Leiden thrombophilia. The protein made by F5 called factor V plays a critical
role in the formation of blood clots in response to injury. The Factor V protein
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. In people with the factor V Leiden mutation,
APC is unable to inactivate factor V normally. As a result, the clotting process
continues longer than usual, increasing the chance of developing abnormal blood
clots.
Information courtesy of: Genetics Home Reference
What are the symptoms of factor V Leiden thrombophilia?
The symptoms of factor V Leiden vary among individuals. There are some individuals
who have the F5 gene and who never develop thrombosis, while others have recurring
thrombosis before the age of 30 years. This variability is influenced by the
number of F5 gene mutation a person has, the presence of other gene alterations
related to blood clotting, and circumstantial risk factors, such as surgery,
use of oral contraceptives and pregnancy.
Symptoms of Factor V Leiden include:
- Having a first DVT or PE before 50 years of age.
- Having recurring DVT or PE.
- Having venous thrombosis in unusual sites in the body such as the brain
or the liver.
- Having a DVT or PE during or right after pregnancy.
- Having a history of unexplained pregnancy loss in the second or third trimester.
- Having a DVT or PE and a strong family history of venous thromboembolism.
The use of hormones, such as oral contraceptive pills (OCPs) and hormone replacement
therapy (HRT), including estrogen and estrogen-like drugs) taken after menopause,
increases the risk of developing DVT and PE. Healthy women taking OCPs have
a three- to four-fold increased risk of developing a DVT or PE compared with
women who do not take OCP. Women with factor V Leiden who take OCPs have about
a 35-fold increased risk of developing a DVT or PE compared with women without
factor V Leiden and those who do not take OCPs. Likewise, postmenopausal women
taking HRT have a two- to three-fold higher risk of developing a DVT or PE than
women who do not take HRT, and women with factor V Leiden who take HRT have
a 15-fold higher risk. Women with heterozygous factor V Leiden who are making
decisions about OCP or HRT use should take these statistics into consideration
when weighing the risks and benefits of treatment.
Information courtesy of: The American Heart Association
How is factor V Leiden thrombophilia diagnosed?
Your doctor would suspect a diagnosis of thrombophilia if you have a history
of venous thrombosis and/or a family history of venous thrombosis. The diagnosis
is made using a screening test called a coagulation screening test or by genetic
testing (DNA analysis) of the F5 gene.
How is factor V Leiden thrombophilia treated?
The management of individuals with factor V Leiden depends on the clinical circumstances. People with factor V Leiden who have had a DVT or PE are usually treated with
blood thinners, or anticoagulants. Anticoagulants such as heparin 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 there are additional risk factors
present. Having had a DVT or PE in the past increases a person?s risk for developing
another one in the future, but having factor V Leiden does not seem to add to
the risk of having a second clot. In general, individuals who have factor V Leiden
but have never had a blood clot are not routinely be treated with an anticoagulant.
Rather, these individuals are counseled about reducing or eliminating other factors
that may add to one?s risk of developing a clot in the future. In addition, these
individuals may require temporary treatment with an anticoagulant during periods
of particularly high risk, such as major surgery.
Factor V Leiden increases the risk of developing a DVT during pregnancy by about
seven-fold. Women with factor V Leiden who are planning pregnancy should discuss
this with their obstetrician and/or hematologist. Most women with factor V Leiden
have normal pregnancies and only require close follow-up during pregnancy. For
those with a history of DVT or PE, treatment with an anticoagulant during a subsequent
pregnancy can prevent recurrent problems.
Information courtesy of: The American Heart Association
What do we know about heredity and factor V Leiden thrombophilia?
Factor V Leiden is the most common inherited form of thrombophilia. The risk
of developing a clot in a blood vessel depends on whether a person inherits
one or two copies of the factor V Leiden mutation. Inheriting one copy of the
mutation from a parent increases by fourfold to eightfold the chance of developing
a clot. People who inherit two copies of the mutation, one from each parent,
may have up to 80 times the usual risk of developing this type of blood clot.
Considering that the risk of developing an abnormal blood clot averages about
1 in 1,000 per year in the general population, the presence of one copy of the
factor V Leiden mutation increases that risk to 1 in 125 to 1 in 250. Having
two copies of the mutation may raise the risk as high as 1 in 12.
Information courtesy of: Genetics Home Reference
Clinical Research on Factor V Leiden Thrombophilia
Currently, NHGRI is not conducting studies on factor V Leiden thrombophilia.
- Current NHGRI Clinical Studies
- Search ClinicalTrials.gov [clinicaltrials.gov]
Currently, one clinical trial is listed as enrolling children with factor
V Leiden. There are currently no trials specifically investigating adults
with factor V Leiden mutations. However, there are several studies enrolling
individuals with thrombosis. To find these clinical trials, visit the link
above and use 'factor V Leiden' or 'thrombosis' as your search terms.
- Clinical Research FAQ
Additional Resources for Factor V Leiden Thrombophilia
- Genetics Home Reference: Factor V Leiden Thrombophilia [ghr.nlm.nih.gov]
The Genetics Home Reference (GHR) provides information about genetic diseases
and associated genes, a glossary of genetic terms, descriptions of genetic
concepts and links to other genetic resources. GHR also has an information
page about the F5 gene, which, when altered, causes factor V Leiden thrombophilia.
- Genetics Home Reference: F5 gene [ghr.nlm.nih.gov]
An information page about the F5 gene, which, when altered, causes factor
V Leiden thrombophilia.
- The American Heart Association [circ.ahajournals.org]
Information from a patient information page on factor V Leiden
- GeneTests and GeneReviews [genetests.org]
Current, expert-authored, peer-reviewed, full-text articles describing the
application of genetic testing to the diagnosis, management, and genetic counseling
of patients with specific inherited conditions.
- The National Heart, Lung, and Blood Institute (NHLBI) [nhlbi.nih.gov]
Provides information on deep vein thrombosis.
- FVL Thrombophilia Support Page [fvleiden.org]
Information on Factor V Leiden Thrombophilia
- The National Alliance for Thrombosis and Thrombophilia [nattinfo.org]
A nationwide, community-based, volunteer health organization committed to
preventing and treating the array of major health problems caused by blood
clots.
- Yahoo! Factor V Leiden Support Group [health.groups.yahoo.com]
A place for support if you have Factor V Leiden.
- United States Centers for Disease Control and Prevention (CDC) [cdc.gov]
Information about a population study on factor V Leiden.
- Factor V Leiden thrombophilia [rarediseases.info.nih.gov]
Information from the Genetics and Rare Diseases Information Center.
- Finding Reliable Health Information Online
A listing of information and links for finding comprehensive genetics health information online.
Last Reviewed: February 25, 2009
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