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Factor V Leiden

There are a number of inherited blood conditions that may increase a person’s chance of developing blood clots in veins. The most common of these is called factor V (five) Leiden

How common is factor V Leiden?

Factor V Leiden is the most common of the inherited clotting disorder and occurs in all races and ethnicities. It is most common in Caucasians from central and northern Europe. The incidence in this population is estimated to be 3 -7 %.

What is factor V Leiden?

Each day we make blood clots to stop bleeding from injury and we break them down. If we did not break clots down we would clot our entire blood system and this would be fatal. The clot removal system is called they fibrinolytic system. It involves cutting up the fibrin web that is the bulk of the blood clot. In factor V Leiden there is a problem with breaking down the clots.

Patients with the factor V Leiden produce an abnormal clotting factor V that is not able to be broken down by protein C. While these individuals clot normally when hurt, the clot breakdown system does not work well so they can form too many blood clots.

How do you test for factor V Leiden?

There are two blood tests used to check for factor V Leiden. One test looks at blood clotting and the other actually looks for the factor V Leiden gene.

How is factor V Leiden inherited?

Genes are present in the center of our cells and come in pairs. We all have two genes that make factor V. Some people inherit one and some have inherit two of the abnormal genes that make Factor V Leiden.

What is the risk of clotting with factor V Leiden?

Blood clots may occur at any age but usually occur in adults. Blood clots are much less common in children, though they may occur.

What are the other risk factors for blood clots?

People who have one factor V Leiden gene have a 7 times increased risk of clots. People who have factor V Leiden genes have a 30 times increased risk of clots.

There are also other risk factors that may increase the likelihood of making blood clots. Children with factor V Leiden who do develop clots almost always have at least one of these additional risk factors. The two most common are:

  • Not moving for long periods of time such as when you are in a cast, have had surgery or are on a long plane or car ride.
  • It is important for you to try to move your legs frequently and avoid sitting for longer than 1-1/2 to two hours at a time.
  • Birth control pills (those with estrogen) or hormone replacement therapy: Talk to your primary care providers or specialist about possible risks and benefits before taking the medication.
  • Other serious medication conditions: These might include diabetes, cancer, lupus, liver disease, kidney disease, etc.

What is the treatment for factor V Leiden?

There is no treatment that can prevent this disorder or make it go away. However, there are things that you can do to reduce your chances of developing a blood clot. In some situations we use a medicine to help prevent clotting (blood thinners) at high-risk times. We ask that patients remain active, control their weight, not smoke and stay well hydrated. Treatment is unique for each person.

What are the signs and symptoms of a blood clot?

The signs and symptoms of a blood clot depends upon the vein involved. When veins in the leg or arm are involved there is often one sided leg or arm pain, swelling, redness and warmth with inability to straighten the leg or arm without pain.

Sometimes, other veins of the body may cause more severe symptoms. Occasionally a part of the clot may break off and travel in the blood stream to the lungs. This is called a pulmonary embolus and can be life threatening. Symptoms of a pulmonary embolus can include shortness of breath, increased or irregular heart rate, chest pain, loss of consciousness or coughing up blood.

Who should be evaluated for factor V Leiden?

Presently it is recommended that anyone with a first degree relative (sister or brother or parent) with factor V Leiden should be tested at or before adolesence.

Additional resources

Thrombosis - Clot Connect:

Thrombosis - Stop The Clot:

Thrombosis - Clot Care:


Reviewed 6/2017

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