What is the definition of Factor V Leiden Thrombophilia?
Factor V Leiden thrombophilia is a genetic disorder that makes it more likely for you to develop a blood clot sometime during your life. Still, it is estimated that 95% of people with factor V Leiden never develop a clot. When a clot does form, the clot most often occurs in your leg (deep venous thrombosis or DVT) or lungs (pulmonary embolism or PE). Factor V Leiden is the name of a specific gene mutation in the F5 gene. This gene plays a role in how your body forms blood clots after an injury. People can inherit one or two copies of the factor V Leiden gene mutation.
This condition should not be confused with Factor V deficiency, an inherited bleeding disorder that can cause excessive bleeding following surgery or trauma.
What are the alternative names for Factor V Leiden Thrombophilia?
- Hereditary resistance to activated protein C
- APC resistance, Leiden type
What are the causes for Factor V Leiden Thrombophilia?
Factor V Leiden thrombophilia is caused by a specific mutation in the F5 or Factor V gene. 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.
What are the symptoms for Factor V Leiden Thrombophilia?
People with factor V Leiden thrombophilia have a higher risk for blood clots. However, the severity of factor V Leiden thrombophilia varies greatly from person to person. Only 5% of people with one factor V Leiden mutation develop a clot by age 65.
The chance a person with a factor V Leiden gene mutation develops a blood clot is affected by a number of factors, such as having a family history of clots, a second factor V Leiden gene mutation, a second genetic or acquired blood clotting disorder, and other non-genetic risk factors. Non-genetic risk factors include surgery, long periods of not moving (like sitting on a long airplane ride), birth control pills and other female hormones, childbirth within the last 6 months, non-O blood group, cancer, and injuries (such as bone fractures).
The most common type of blood clots associated with factor V Leiden thrombophilia, are deep venous thrombosis or DVT and pulmonary embolism or PE. Signs and symptoms of DVT include leg pain, tenderness, swelling, increased warmth or redness in one leg. Signs and symptoms of pulmonary embolism usually include cough, chest pain, shortness of breath or rapid heartbeat or breathing. To learn more about the symptoms of DVT and PE, click here.
While less common, other possible sites of blood clots, include superficial veins of the leg, veins carrying blood from the digestive organs and spleen to the liver, veins carrying blood away from the liver, and veins supplying the brain. Factor V Leiden thrombophilia may contribute a small amount of risk toward a heart attack, stroke, or pregnancy complication.
What are the current treatments for Factor V Leiden Thrombophilia?
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.
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).
Is Factor V Leiden Thrombophilia an inherited disorder?
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.