Factor V (Leiden) is located on chromosome 1 (1q24.2). The Factor 5 mutation is the replacement of the G nucleotide at position 1691 of this gene with the A nucleotide (G1691A) and the substitution of a single amino acid (Arg506Gln) in one of the three separate APC opening regions of the Factor 5 molecule. Thrombophilia represents a weak anticoagulant response to activated protein C (APC) and an increased risk of venous thromboembolism.
What is Factor V Leiden Thrombophilia?
Factor V Leiden Thrombophilia is a genetic blood clotting disorder. Factor V Leiden is the name for a genetic change that causes a risk of thrombophilia, or a tendency to form abnormal blood clots in the blood vessels. In cases with factor V leiden mutation, the risks are above average for a type of clot that forms in the great veins (venous) of the legs (we call it deep vein thrombosis or DVT) or a type of clot that is transported through the bloodstream and settles in the lungs (we call it Pulmonary Embolism or PE).
Factor 5 Leiden is the most common inherited coagulation disorder. Among whites of the American and European races, 3 to 8% carry one copy of the Factor V Leiden mutation and 1/5,000 two copies of the mutation. This mutation is less common in other breeds.
A mutation in the Factor 5 gene (F5) increases the risk of developing Factor 5 Leiden thrombophilia. The protein made by F5, called Factor V, plays a critical role in blood clot formation, which develops in response to injury. Factor V protein participates in a series of chemical reactions that keep blood clots together. A molecule called activated protein C (APC) inactivates Factor 5, preventing blood clots from getting too large. In people with a Factor V Leiden mutation, APC cannot normally inactivate Factor V. As a result, the clotting process takes longer than normal, increasing the likelihood of developing an abnormal blood clot.
What are the Symptoms of Factor V Leiden Thrombophilia?
Factor V Leiden symptoms can vary from person to person. While there are people who have the F5 gene but never develop thrombosis, sometimes recurrent thrombosis can occur before the age of 30. This difference may be affected by the number of Factor 5 mutations the person has, the presence of other gene changes related to blood coagulation, and influencing factors such as surgery, oral contraceptive use, and pregnancy.
Main Factor V Leiden Symptoms:
- First Deep Vein Thrombosis (DVT) or Pulmonary Embolism (PE) before age 50.
- Having recurrent DVT or PE.
- Venous thrombosis in unusual organs such as the brain or liver.
- A case of unexplained pregnancy loss in the first, second or third trimester.
- DVT or PE occurring during or shortly after pregnancy.
- A history of DVT or PE and a strong family history of venous thromboembolism.
The use of birth control pills (OC) and hormone-regulating therapy (HRT), and the use of drugs containing post-menopausal hormone drugs increase the risk of developing DVT and PE. Healthy women who use contraceptives have a 3-4 times greater risk of developing DVT or PE compared to women who do not.
Women who have a Factor 5 Leiden mutation and use birth control drugs have an approximately 35-fold increased risk of developing DVT or PE than women without a Factor V Leiden mutation and who do not use OCs.
Similarly, postmenopausal women using hormone-regulating therapy have a 2-3-fold increased risk of developing DVT or PE compared to women not using HRT, and women with Factor V Leiden mutations are 15-fold higher on hormone-regulating therapy.
Those with a heterozygous Factor V Leiden mutation who decide to use OC or hormone-regulating therapy should take these statistics into account when assessing the risk-benefit of therapy.
How to diagnose Factor V Leiden thrombophilia?
If you have a history of venous thrombosis, that is, a history of clot formation in the veins of the legs and / or a family history of venous thrombosis, your doctor will suspect the formation of thrombophilia. This diagnosis is made using screening tests called coagulation screening test or F5 (Factor 5) gene genetic test (DNA analysis).
How is Factor V Leiden Thrombophilia Treated?
The treatment of factor 5 Leiden patients depends on the clinical conditions. Factor V Leiden patients with Deep Vein Thrombosis or Pulmonary Embolism are usually treated with anticoagulants or anticoagulants. Anticoagulants (clot inhibitors) such as heparin etc. are given at different times and doses depending on the condition of the person.
It is generally not recommended that patients with Factor V Leiden be treated with anticoagulants for life only if they have had a DVT or PE, unless there are additional risk factors. Having a DVT or PE in the past increases a person’s risk of having it again in the future, but having the Factor 5 Leiden mutation does not additionally increase the risk of a second clot.
In general, people with the Factor 5 Leiden mutation but who have not developed a blood clot condition are not routinely treated with an anticoagulant. Instead, these people are counseled to reduce or eliminate other factors that may add to their risk of developing a clot in the future. In addition, these individuals may need to be treated temporarily with an anticoagulant during particularly high-risk periods, such as major surgery.
Factor V Leiden increases the risk of developing a DVT during pregnancy about seven times. Women with a factor V Leiden mutation who are planning a pregnancy should discuss this with their obstetricians and/or haematologists. Most women with a factor V Leiden mutation have normal pregnancies and only need close monitoring during pregnancy. For those with a history of DVT or PE, treatment with an anticoagulant during subsequent pregnancy can prevent recurrent problems.
About Genetics and Factor 5 Leiden Thrombophilia ?
Factor 5 Leiden is the most common form of hereditary thrombophilia. The risk of a blood clotting in a vein is related to a person carrying one or two copies of the Factor V Leiden mutation.
Having one copy of the mutation from the mother or father increases the risk of clot formation 5-10 times. Having one copy of the mutation from each parent can increase a person’s overall risk of developing this type of blood clot by up to 80 times.
Considering that the risk of developing abnormal blood clots in individuals is 1/1000 on average in the general population, a copy of Factor V Leiden mutation increases this risk to 1/125 – 1/250.
Exp.Dr. R. Filiz Dilmegani
Istanbul Laboratories
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