Factor V Leiden Thrombophilia

Factor V Leiden thrombophilia is an inherited blood clotting disorder. This means you’re born with a gene change that makes your blood more likely to clot when it shouldn’t. You have a higher risk than those without this condition of developing:

• Deep vein thrombosis (DVT). This is the formation of blood clots in your deep veins. Usually, these form in leg or arm veins. But they can also develop in veins in your liver, kidneys, brain or eyes.
• Pulmonary embolism (PE). This is a blood clot that travels through your bloodstream to one of your lungs.

Having this condition doesn’t automatically mean you’ll develop DVT or PE. In fact, the vast majority of people (9 out of 10) never develop abnormal blood clots. But the disorder raises your risk compared to people without the disorder.

The prevalence of factor V Leiden varies by ethnicity. In general, it’s more common among people who are white in the U.S. and Europe.

In the U.S., this disorder affects:

• About 5 in 100 people of European descent
• About 2 in 100 Hispanic people
• About 1 in 100 people who are Black or Native American
• Fewer than 1 in 100 people of Asian descent

Around 1 in 5 people who develop a blood clot in their veins have the factor V Leiden variant.

This condition’s name is pronounced “FAK-ter five LYE-den.” The “V” stands for the number five in Roman numerals.

Symptoms of factor V Leiden thrombophilia

The gene change itself doesn’t cause any symptoms. It’s possible to have this disorder and never even know it. But you may develop symptoms if a blood clot forms.

If you have symptoms of DVT or a PE, call 911 or your local emergency number. Or ask someone to drive you to the nearest emergency room.

Symptoms of deep vein thrombosis include:

• Swelling, warmth and skin color changes in your leg or arm
• Tenderness or pain in your leg or arm
• Larger-than-normal veins near your skin’s surface
• Pain in your belly or flank (if blood clots affect veins in your abdomen)
• Severe, sudden headache and/or seizures (if blood clots affect veins in your brain)

Symptoms of a pulmonary embolism include:

• Sudden shortness of breath
• Sharp chest pain that feels worse when you take deep breaths, cough or sneeze
• Cough, which may produce blood
• Wheezing
• Fast heartbeat (tachycardia)
• Feeling anxious
• Feeling lightheaded or fainting

Causes of factor V Leiden thrombophilia

A gene variant causes factor V Leiden. “Coagulation factor V” is the name of a protein that helps your blood clot when needed, like after an injury. Your F5 gene tells your body how to make this protein.

Most people are born with two normal copies of the F5 gene. But if you inherit an abnormal copy, you have the factor V Leiden variant (sometimes called a mutation). “Leiden” is the city in the Netherlands where researchers discovered this gene variant.

The factor V Leiden variant tells your body to make a protein that has one small change in its structure. This change makes the protein resist other proteins (protein C and protein S) that stop excessive clotting. Without this check, factor V can make your blood clot when it shouldn’t.

Does this pass down within families?

Yes. You inherit this condition from one or both of your biological parents. Factor V Leiden follows an autosomal dominant inheritance pattern. That means only one of your parents has to pass the gene variant on to you for you to inherit it.

Most people with factor V Leiden inherit just one abnormal gene copy (heterozygous). Rarely, you can inherit two abnormal gene copies — one from each parent (homozygous).

Risk factors for developing a blood clot

You’re more likely to develop a blood clot if you:

• Inherited two copies of an abnormal F5 gene (homozygous)
• Have a history of DVT or PE in your biological family
• Have additional blood clotting disorders
• Undergo surgery
• Are pregnant
• Take estrogen-based therapies like certain forms of contraception or hormone replacement therapy

Talk to your healthcare provider about your risk for developing blood clots and what precautions you should take.

Complications of this condition

If you have factor V Leiden thrombophilia, you may experience:

• DVT or a PE before age 50
• Multiple episodes of DVT or PE
• Blood clots in less commonly affected veins, like those in your liver or brain
• DVT or a PE during pregnancy or postpartum
• DVT or a PE soon after starting birth control pills or hormone therapy

How doctors diagnose this condition

Blood tests (including genetic testing) can show if you have factor V Leiden thrombophilia. Your healthcare provider may suggest testing for the condition if:

• You have a history of DVT or PE, particularly at a younger age than expected
• One or more of your biological family members have a history of blood clots

How is factor V Leiden thrombophilia treated?

It’s a lifelong condition. There’s no cure or treatment for the gene variant itself. Instead, treatment involves breaking up any blood clots that form and lowering your risk of future clots. Your provider may recommend:

• Anticoagulant medication (blood thinners) to break up clots and prevent new ones
• Compression stockings to improve blood flow in your legs and lower the risk of clots
• Placement of a vena cava filter to prevent blood clots from traveling to your lungs
• Surgery to remove blood clots

How long you need to take blood thinners depends on your risk of blood clots coming back. Some people only need to take them for a few months. Others need them long term. Your provider will explain the best treatment plan for you.

When should I see my healthcare provider?

Visit your provider for a yearly checkup. If you’ve been diagnosed with DVT or a PE, you’ll have frequent follow-up appointments so your provider can check treatment progress. If you’re taking warfarin, you’ll need routine blood testing (prothrombin time test) to check how well your medication is working.

It’s also important to talk to your provider:

• Before using contraception or hormone replacement therapy
• Before becoming pregnant

What is the life expectancy of someone with factor V Leiden?

Factor V Leiden doesn’t affect life expectancy in most people. Even if you develop a blood clot, prompt treatment can prevent a fatal outcome. It’s important to talk to your provider about any concerns you have related to life expectancy or future complications.

What should I avoid if I have factor V Leiden?

Your healthcare provider will tailor advice to your needs. In general, you should avoid:

• Smoking, vaping and other tobacco use
• Long periods of sitting
• Drinking too much alcohol, or drinking any alcohol on long plane flights
• Using estrogen-based contraception and hormone replacement therapy (talk to your provider first)

What’s the difference between factor V deficiency and factor V Leiden thrombophilia?

These are two different genetic conditions. Both conditions involve changes to the F5 gene. With factor V Leiden, the change makes your blood clot too easily. But with factor V deficiency, the change stops your blood from clotting when it should.

Factor V deficiency is a rare bleeding disorder that affects about 1 in 1,000,000 people. It can involve recurrent nosebleeds, heavy menstrual bleeding and prolonged bleeding after surgery.