What is Factor V Leiden?
Factor V Leiden is the name of a specific gene mutation of the factor V gene. The factor V gene provides your body with instructions on how to make the factor V protein.
This protein is found in your blood and is needed for your blood to clot properly.
The mutation of the factor V gene (Factor V Leiden) causes the body to make an altered form of the factor V protein that results in an increased tendency to form abnormal blood clots that can block blood vessels.
This condition when blood clots are more likely to form is called thrombophilia. Factor V Leiden is a genetic disorder meaning it is in your genes and you were born with it.
Therefore, if you have the Factor V Leiden mutation, you have an inherited thrombophilia or genetic blood clotting disorder. This is called Factor V Leiden thrombophilia.
Factor V Leiden is the most common inherited form of thrombophilia. Millions of people in the United States and the world carry the Factor V Leiden gene. 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.
Although Factor V Leiden thrombophilia increases the risk of blood clots, only about 10 percent of individuals with the gene mutation ever develop abnormal clots.
However, for the people who do, these abnormal blood clots can lead to long-term health problems or become life threatening if they break loose and travel to the lungs.
Tell me more about Factor V Leiden
- Factor V Leiden is pronounced “factor five Li’-den”. The letter “V” is the Roman numeral for the number five.
- Factor V is a natural protein found in the blood of humans.
- The factor V protein is just one of many special proteins called clotting factors that are needed to help your blood clot properly in the event of an injury to a blood vessel.
- Some people do not have the normal factor V protein.
- They have a different form of the protein called Factor V Leiden.
- This different form of the protein or Factor V Leiden is caused by a change (mutation) in the DNA in the gene used to make the factor V protein.
- Genes are tiny parts of cells that tell the cells how to grow.
- Factor V Leiden is defined as a DNA mutation in the gene used to make the factor V protein.
- Thus, Factor V Leiden is a genetic disorder meaning it is in your genes and you were born with it.
- The different or mutated gene that makes the Factor V Leiden protein is inherited from one or both of your parents.
- Factor V Leiden is not a disease but a genetic disorder.
- Factor V Leiden is not contagious meaning it cannot be transmitted from person to person through contact.
- Factor V Leiden is a relatively common condition.
- This disorder occurs in both men and women.
- This disorder is most common in people who are Caucasian (white) and of European decent (those who can trace their heritage back to Europe).
- Since Factor V Leiden is an inherited disorder, there is a chance your children, brothers, sisters and other direct relatives may have also inherited the mutated gene.
- The mutation is named after a city called Leiden in the Netherlands where researchers first identified the gene mutation at Leiden University in 1994.
How did I get Factor V Leiden?
If you have Factor V Leiden, you inherited either one copy or two copies of the defective gene from your parents.
- Genes are present in our cells and come in pairs.
- Everyone has two copies of the Factor V gene.
- We inherit one gene from our mother and one gene from our father.
- One or both of these genes can be mutated and cause the Factor V Leiden protein to be made.
Heterozygous Factor V Leiden
- If you inherited one Factor V Leiden gene from one parent, you have the heterozygous type of Factor V Leiden.
- You have one Factor V Leiden gene from one parent and one normal Factor V gene from your other parent.
- In your body, you have 50% Factor V Leiden and 50% normal Factor V.
- This happens in about 5 out of 100 people of Caucasian decent.
- Inheriting one copy of the Factor V Leiden gene slightly increases your risk of developing blood clots.
Homozygous Factor V Leiden
- If you have two Factor V Leiden genes, you have the homozygous type of Factor V Leiden.
- You inherited one Factor V Leiden gene from your mother and one Factor V Leiden gene from your father.
- In your body, you have 100% of Factor V Leiden and no normal Factor V.
- This happens in less than 1 out of 100 people of Caucasian decent.
- Inheriting two copies of the Factor V Leiden gene significantly increases your risk of developing blood clots.
What are the effects of having Factor V Leiden?
If you have Factor V Leiden, you have a greater chance or tendency of developing venous blood clots.
- Factor V Leiden doesn’t cause blood clots but increases your chances of getting a blood clot.
- The blood clots associated with Factor V Leiden are almost always activated or triggered by a precipitating catalyst such as surgery, trauma, immobility, use of hormones, etc.
- Researchers aren’t clear why some people (about 10%) with Factor V Leiden develop blood clots while others with Factor V Leiden do not experience blood clots associated with the disorder.
- Not all blood clots are caused by or related to Factor V Leiden and people who do not have Factor V Leiden still suffer from blood clots.
- Blood clots associated with Factor V Leiden typically form in the veins. This is known as a venous thromboembolism or VTE.
- Some clots do not cause damage and disappear on their own.
- Other abnormal clots can lead to long-term health problems or become life threatening if they break loose and travel to the lungs.
- Blood clots related to Factor V Leiden typically form in the deep veins of the legs. These are called a deep vein thrombosis or a DVT.
- Blood clots that move from other parts of the body to the lungs are called pulmonary embolus or PE. A pulmonary embolism can be life threatening.
- Although blood clots caused by Factor V Leiden typically form in the legs, they can form anywhere throughout the body. Other locations include the brain, eyes, kidneys, and liver.
- Blood clots caused by Factor V Leiden may occur at any age but usually occur in adults.
- Women who carry the genetic mutation may have an increased tendency to develop blood clots during pregnancy or when taking the hormone estrogen.
- Blood clots are much less common in children, although they may occur.
How does Factor V Leiden affect blood clotting?
Factor V is one of the proteins needed to make blood clots form. In the normal blood clotting process, another protein “turns off” the clotting activity of factor V when clotting is no longer needed. The mutated Factor V Leiden protein is harder to “turn off” than the normal factor V protein. As a result, clotting continues for an excessive period of time and sometimes leads to an enlarged or abnormal blood clot.
- When you are injured, blood clotting cells (platelets) are drawn to the site of the injury in the blood vessel.
- Enzyme reactions occur on the surface of the platelets to generate net-like strands of fibrous material called fibrin. Fibrin acts as a biological “band-aid” to hold the platelets firmly to the injured site and prevent blood from leaking out.
- This combination of platelets and fibrin is called a clot.
- Factor V is a protein or clotting factor that helps create the enzyme reactions that form the fibrin in the clot.
- People with Factor V Leiden make an altered factor V protein as a result of a mutated gene.
- The clot remains in place while other enzymes repair the damaged blood vessel.
- The clotting action of factor V is controlled by other proteins in the blood such as protein C and protein S. One of those proteins is called Activated protein C or APC.
- When enough fibrin has been made, activated protein C (APC) inactivates factor V, helping stop the clot from growing any larger than necessary.
- The altered Factor V Leiden protein is completely normal in terms of its ability to form a clot to prevent bleeding.
- The difference with the Factor V Leiden protein is that it is harder to inactivate or “turn off” the clotting action than it is with the normal factor V protein.
- Thus, Activated Protein C does not work as well on the Factor V Leiden protein.
- Factor V Leiden “resists” or is resistant to being degraded or inactivated by Activated Protein C, so it takes longer to turn off the clotting action.
- As a result, Factor V Leiden lingers in the circulation longer and can contribute to the formation of abnormal blood clots.
- This is why Factor V Leiden is sometimes called Activated Protein C Resistance or APC Resistance and why people with this mutation have a tendency to form blood clots more than people without it.
- This condition when blood clots are more likely or have an increased tendency to form is called thrombophilia.
- If you have the Factor V Leiden mutation, you have an inherited thrombophilia or blood clotting disorder.
How was Factor V Leiden discovered?
The mutation is named after a city called Leiden in the Netherlands where researchers first identified the gene mutation at Leiden University in 1994.
- What are the symptoms of Factor V Leiden?
- How is Factor V Leiden Diagnosed?
- How is Factor V Leiden Treated?
- How serious is Factor V Leiden?
- What are the chances of developing a blood clot?
- How do they test for Factor V Leiden?
- Who should be tested for Factor V Leiden?
- Frequently Asked Questions about Factor V Leiden.
- What is known about what “triggers” Factor V Leiden to cause blood clots?