Overview
Factor V Leiden (FAK-tur five LIDE-n) is a change of one of the clotting factors in the blood. A clotting factor is a protein that helps blood to clot. This change can raise the risk of getting harmful blood clots, most often in the legs or lungs.
Most people with factor V Leiden never get harmful clots. But people who do get them need to take blood thinners. Blood clots can lead to long-term health issues. And they can be life-threatening.
People assigned male at birth or female at birth can have factor V Leiden. People who carry the changed gene in factor V Leiden may be more likely to get blood clots during pregnancy or when taking the hormone estrogen.
There is treatment for people who have factor V Leiden and get blood clots. Anticoagulant medicines, also called blood thinners, can lower the risk of getting more blood clots and having serious complications.
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Symptoms
Having changed gene that causes factor V Leiden itself doesn't cause symptoms. Getting a blood clot in the legs or lungs may be the first sign of having the condition.
Some clots do no damage and go away on their own. Others can be life-threatening. Symptoms of a blood clot depend on what part of the body it affects.
A clot in a deep vein
This is known as deep vein thrombosis, also called DVT. This most often happens in the legs. A clot in a deep vein may not cause symptoms. If there are symptoms, they may include:
- Pain.
- Swelling.
- Redness. This may be harder to see on Black skin or brown skin.
- Warmth.
A clot that travels to the lungs
This is called a pulmonary embolism. It happens when part of a clot in a deep vein breaks free and travels through the right side of the heart to the lung. In the lung, it blocks blood flow. This can be life-threatening.
Symptoms may include:
- Sudden shortness of breath.
- Chest pain when breathing in.
- A cough that makes bloody or blood-streaked mucus.
- Rapid heartbeat.
When to see a doctor
Seek medical help right away if you have symptoms of either a deep vein thrombosis or a pulmonary embolism.
Causes
People who have factor V Leiden get either one copy or, rarely, two copies of the changed gene from their parents. Having one copy of the changed gene slightly raises the risk of getting blood clots. Getting two copies, one from each parent, greatly raises the risk of getting blood clots.
Risk factors
A family history of factor V Leiden raises the risk of getting the condition. The condition is most common in people who are white and whose families are from Eastern Europe.
People who get the factor V Leiden gene change from only one parent have a 5% chance of getting a blood clot by age 65. Factors that raise this risk include:
- Two changed genes. Getting the changed genes from both parents instead of just one can greatly raise the risk of blood clots.
- Not moving.. Long periods of not moving, such as sitting during a long airplane flight, can raise the risk of leg clots.
- The hormone estrogens. Birth control pills, hormone replacement therapy and pregnancy can raise the risk of getting blood clots.
- Surgeries or injuries. Surgeries or injuries such as broken bones can raise the risk of blood clots.
- Certain blood types. People who have blood types A, B or AB have a higher risk of blood clots than those with blood type O.
Complications
Factor V Leiden can cause blood clots in the legs, called deep vein thrombosis, and lungs, called pulmonary embolism. These blood clots can be life-threatening.