This inherited clotting disorder can increase your chance of developing abnormal blood clots, most commonly in your legs or lungs.
Factor V Leiden (FAK-tur five LIDE-n) is a mutation of one of the clotting factors in the blood. This mutation can increase your chance of developing abnormal blood clots, most commonly in your legs or lungs.
Most people with factor V Leiden never develop abnormal clots. But in people who do, these abnormal clots can lead to long-term health problems or become life-threatening.
Both men and women can have factor V Leiden. Women who carry the factor V Leiden mutation may have an increased tendency to develop blood clots during pregnancy or when taking the hormone estrogen.
If you have factor V Leiden and have developed blood clots, anticoagulant medications can lessen your risk of developing additional blood clots and help you avoid potentially serious complications.
The factor V Leiden mutation does not itself cause any symptoms. Since factor V Leiden is a risk for developing blood clots in the leg or lungs, the first indication that you have the disorder may be the development of an abnormal blood clot.
Some clots do no damage and disappear on their own. Others can be life-threatening. Symptoms of a blood clot depend on what part of your body is affected.
This is known as deep vein thrombosis (DVT), which most commonly occurs in the legs. A DVT may not cause any symptoms. If signs and symptoms do occur, they can include:
Known as a pulmonary embolism, this occurs when a portion of a DVT breaks free and travels through the right side of your heart to your lung, where it blocks blood flow. This can be a life-threatening situation. Signs and symptoms may include:
Seek medical attention immediately if you have signs or symptoms of either a DVT or a pulmonary embolism.
If you have factor V Leiden, you inherited either one copy or, rarely, two copies of the defective gene. Inheriting one copy slightly increases your risk of developing blood clots. Inheriting two copies — one from each parent — significantly increases your risk of developing blood clots.
A family history of factor V Leiden increases your risk of inheriting the disorder. The disorder is most common in people who are white and of European descent.
People who have inherited factor V Leiden from only one parent have a 5 percent chance of developing an abnormal blood clot by age 65. Factors that increase this risk include:
Factor V Leiden can cause blood clots in the legs (deep vein thrombosis) and lungs (pulmonary embolism). These blood clots can be life-threatening.
Your doctor may suspect factor V Leiden if you've had one or more episodes of abnormal blood clotting or if you have a strong family history of abnormal blood clots. Your doctor can confirm that you have factor V Leiden with a blood test.
Doctors generally prescribe blood-thinning medications to treat people who develop abnormal blood clots. This type of medicine usually isn't needed for people who have the factor V Leiden mutation but who have not experienced abnormal blood clots.
However, your doctor might suggest that you take extra precautions to prevent blood clots if you have the factor V Leiden mutation and are going to have surgery. These precautions might include:
Some precautions to help reduce your risk of blood clots include:
If your factor V Leiden requires you to take anticoagulant medication, here are some steps that might help you prevent injury and avoid excessive bleeding:
Your doctor may refer you to a specialist in genetic disorders (geneticist) or a specialist in blood disorders (hematologist) for testing to determine whether the cause of your blood clots is genetic and, specifically, whether you have factor V Leiden.
Here's some information to help you prepare for your appointment.
For factor V Leiden, some basic questions to ask your doctor include:
If your doctor recommends genetic testing, some questions you might want to ask the genetic specialist include: