Factor V Leiden is an inherited blood clotting disorder that raises your risk of deep vein thrombosis or a pulmonary embolism. A mutation in your F5 gene causes this disorder, which follows an autosomal dominant inheritance pattern. Most people with this disorder never develop a blood clot. But if you do, prompt treatment can manage your condition.
Factor V Leiden (pronounced “FAK-ter five LYE-den”) is a blood clotting disorder that raises your risk of abnormal blood clots. It’s the most common blood clotting disorder that’s inherited, or passed down within biological families.
People with factor V Leiden have a mutation in their coagulation factor V (F5) gene. Your F5 gene controls the production of a protein called factor V, which helps your blood clot when needed (such as after an injury). The factor V Leiden mutation changes this protein’s structure. This change causes it to resist other proteins that stop excessive clotting. As a result, your blood may clot more easily than it should, leading to serious complications.
Factor V Leiden makes you more likely to develop:
It’s important to know that people with factor V Leiden won’t necessarily develop DVT or PE. In fact, the vast majority (9 out of 10) never develop abnormal blood clots. However, the disorder raises your risk compared to people without the disorder.
If you have this disorder, you may experience:
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:
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A genetic mutation (change) causes factor V Leiden. People with this condition have a factor V Leiden mutation, meaning there’s a change in their coagulation factor V (F5) gene. This gene carries instructions that tell your body how to properly create the factor V protein.
Researchers have found that the factor V Leiden mutation involves one small change in the protein’s structure. This change causes factor V to resist the actions of other proteins (protein C and protein S), which normally inactivate factor V when needed to keep your blood from clotting abnormally. As a result, factor V works in overdrive, making your blood more likely to clot when it shouldn’t.
You inherit this condition from one of your biological parents. Factor V Leiden follows an autosomal dominant inheritance pattern. That means only one of your parents has to pass the genetic mutation on to you in order for you to inherit it.
You’re at risk for having factor V Leiden if one of your parents carries a copy of the mutated F5 gene.
If you have the disorder, you may never develop a blood clot. But some factors raise your risk of developing clots. These include:
Talk to your healthcare provider about your risk of developing blood clots and what precautions you should take.
The factor V Leiden mutation itself doesn’t cause any symptoms. Most people who inherit it never develop abnormal blood clots, and may never even know they have the disorder. You can have a family history of deep vein thrombosis (DVT) or pulmonary embolism (PE) but never develop either yourself.
However, some people with this disorder develop DVT or PE. It’s important to learn the symptoms so you can seek immediate medical care.
Symptoms of deep vein thrombosis include:
Symptoms of a pulmonary embolism include:
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.
Factor V Leiden may lead to deep vein thrombosis or a pulmonary embolism, which are serious medical emergencies. However, most people with this genetic mutation never develop these complications.
Some research shows that factor V Leiden impacts pregnancy. This disorder may raise your risk of a miscarriage or other complications. But there’s no clear consensus, and researchers continue to explore what risks, if any, factor V Leiden poses during pregnancy.
Laboratory testing (blood tests) diagnose this disorder. Your healthcare provider may suspect you have factor V Leiden if you have a history of venous thromboembolism. They may also suspect it if one or more of your biological family members have a history of blood clots.
If your provider feels it’s warranted, they’ll order blood tests, including:
Simply having a family history of blood clots may not be reason enough to run these tests. Your provider will advise you on whether you need testing, as well as on the pros and cons of testing.
The factor V Leiden mutation itself doesn’t have any specific treatment. But when a person is diagnosed with an acute deep vein thrombosis (DVT) or pulmonary embolism (PE), treatment with anticoagulants (blood thinners) will be necessary and should be started as soon as possible. Depending on the severity of symptoms, other treatments may be necessary as well. Often, those treatments will require hospitalization.
Individuals who happen to know that they have factor V Leiden — but have never had blood clots — don’t have to be prescribed any blood thinners. But it’s important that these individuals discuss with their doctors what they should be aware of — and what they can do to minimize — the risk of DVT or PE. Some issues that can be discussed with your doctor include:
Other than the increased risk of developing DVT or PE, factor V Leiden may increase the risk of miscarriage or other pregnancy complications, such as preeclampsia and eclampsia, placental abruption (when the placenta separates too early from the wall of your uterus), and having a fetus that grows slower than is usual. Miscarriages associated with factor V Leiden are more likely to occur later in pregnancy (after the first trimester).
But because there are many risk factors associated with the development of those pregnancy complications, there’s still debate and uncertainty as to how much the factor V Leiden mutation is a cause or just another contributing factor to those pregnancy complications.
No, you can’t prevent this blood clotting disorder. There currently aren’t any genetic treatments that can stop someone from inheriting a mutated F5 gene.
Most people who have this disorder never develop blood clots or have pregnancy complications. But you should talk to your provider about what you can expect in your individual situation.
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.
Talk to your healthcare provider to receive advice tailored to your needs. In general, you should avoid:
You can help lower your risk of blood clots with lifestyle changes, including:
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 important to go to all of your appointments and talk to your provider about any questions or concerns you have.
It’s also important to talk to your provider:
Seek emergency medical care if you develop symptoms of deep vein thrombosis or a pulmonary embolism. These conditions can be life-threatening and require immediate medical treatment. The sooner you receive care, the better your chances of a good outcome.
If you have factor V Leiden, you may have many questions. Here are a few to help you start the conversation:
Factor V is a coagulation factor, or protein, in your blood. Factor V and other proteins work together to help your blood clot when necessary. These proteins are essential helpers that support hemostasis. This is your body’s reaction to an injury that prevents you from bleeding too much. But if you have a blood clotting disorder, your blood forms clots more easily than normal.
Factor V Leiden is the name of one such blood clotting disorder. This disorder affects factor V, as opposed to other proteins in your blood. “Leiden” is the city in the Netherlands where researchers discovered the condition.
A note from Cleveland Clinic
If you or a loved one have factor V Leiden, you might feel scared about what the future will bring. Maybe you’ve already had to deal with a blood clot and wonder if you’ll face another. Or maybe you’ve had no issues, but your loved one needed treatment for DVT. You’re might be wondering, “Will this happen to me? What are my risks? What about my children?”
The questions may keep coming, and that’s normal. As they come, write them down. Take your questions to your healthcare provider and get the answers you need. It may ease your mind to know that most people with this disorder never have a blood clot. But if you do develop clots, be assured there are treatments that can help. Following your provider’s guidance can help you catch and resolve problems early before they interrupt the flow of your life.
Last reviewed by a Cleveland Clinic medical professional on 10/04/2022.
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