The prothrombin gene mutation can make you more likely to get harmful blood clots, but you may never get one. Medicines help treat and prevent blood clots in people who are high risk for them. You should know the warning signs of a problematic blood clot so you can identify it and get help.
Prothrombin gene mutation (or Factor II mutation or Prothrombin G20210A) is an inherited condition that increases your predisposition to develop abnormal blood clots in the veins (deep vein thrombosis or DVT) and lungs (pulmonary embolism or PE). This happens because your body makes more of the Factor II (prothrombin) protein than you need for normal clot formation. Blood clots can cause serious problems in your body when they block blood flow, keeping oxygen from getting to your cells.
You may inherit an abnormal Factor II gene from one or both parents. If you get the mutation from both of your parents, you are homozygous (you have two abnormal copies of the Factor II gene). If you get the mutation from one of your parents, you are heterozygous (you have only one abnormal copy of the Factor II gene, but the gene from your other parent is normal).
In heterozygous carriers of this mutation, the risk of developing a deep vein thrombosis or pulmonary embolism is about two to three in 1,000. That risk is several times higher in homozygous carriers.
If you are homozygous, you will pass the mutation on to your children.
If you are heterozygous, there’s a 50% chance that your children will get the mutation.
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About 1 in every 50 white people in Europe and North America has the heterozygous prothrombin gene mutation, making it the second most common inherited clotting disorder. Factor V Leiden is the most common one. About 1 of every 250 Black people in America has the prothrombin gene mutation.
You may have a higher risk of getting:
Although the prothrombin gene mutation is the second most common inherited predisposition to a deep vein thrombosis or pulmonary embolism, it is the weakest of all inherited clotting disorders in terms of risk of causing abnormal blood clots. In addition, this mutation only increases the risk of vein clots (deep vein thrombosis or pulmonary embolism). It does not increase the risk of myocardial infarction (heart attacks) or arterial strokes.
The mutation does not cause any symptoms in and of itself. You probably won’t know you have prothrombin gene mutation unless you have a specific blood test if/after you develop a deep vein thrombosis or pulmonary embolism. The majority of people born with this mutation will not develop an abnormal blood clot in their lifetime.
Symptoms of deep vein thrombosis in your arm or leg include:
Symptoms of a pulmonary embolism (located in your lung) include:
It is a genetic mutation in your Factor II gene that makes it create too much prothrombin (coagulation factor II), and you end up with a higher risk of developing blood clots than someone with a normal prothrombin gene.
Other things can add to your blood clot risk, including:
You’ll need a specific blood test to check for the prothrombin gene mutation. Your provider may think you have a clotting problem if you:
There is no specific treatment for the mutation itself. At this time, we can’t treat or change our genes.
But your provider can help you keep your blood from clotting too much. If you’re having a deep vein thrombosis or pulmonary embolism, your provider will typically treat you with anticoagulants (blood thinners) and occasionally with thrombolytic (“clot-busting”) medicines. In rare cases, you may need a catheter procedure or surgery to remove the bulk of the clots.
There is no specific treatment for the mutation itself.
If you develop a deep vein thrombosis or pulmonary embolism, your provider will prescribe an anticoagulant. The length of treatment may vary depending on your situation. Some people only need treatment for three months, but others will need blood thinner treatment indefinitely.
If you’re taking anticoagulants (blood thinners), be aware that you may bleed or bruise more easily, which is why it is very important to have regular follow-up medical appointments with your provider.
Symptoms of a deep vein thrombosis or pulmonary embolism typically start getting better soon after specific treatment is started. Symptoms may resolve within days or months, depending on the location and severity of your deep vein thrombosis or pulmonary embolism.
Because it’s an inherited condition, you can’t prevent the prothrombin gene mutation. However, you can reduce your risk of a deep vein thrombosis or pulmonary embolism if you:
The majority of people who have the prothrombin gene mutation don’t get a dangerous blood clot and the mutation doesn’t cause deep vein thrombosis or pulmonary embolism in the vast majority of pregnancies.
You’ll have the prothrombin gene mutation for life, since it’s part of your genetic makeup.
You will most likely not have a dangerous blood clot, but your provider can provide counseling on how to reduce the risk of a deep vein thrombosis or pulmonary embolism.
You may not need to do anything other than lead a healthy lifestyle to minimize the risk of a deep vein thrombosis or pulmonary embolism.
If you’ve had a deep vein thrombosis or pulmonary embolism before and know you have the prothrombin gene mutation, you may need a prescription for low-dose (preventive doses) of an injectable blood thinner (such as heparin or a low-molecular-weight heparin) during your pregnancy and for a few weeks after delivery. Both of those types of injectable blood thinners are safe for your baby.
But not everyone with the prothrombin gene mutation and a history of deep vein thrombosis or pulmonary embolism needs blood thinners during pregnancy. It depends on the specific details of the previous deep vein thrombosis or pulmonary embolism.
If you have the prothrombin gene mutation but never had a deep vein thrombosis or pulmonary embolism before, you will not need a blood thinner during or after pregnancy.
Yes, you may be able to donate blood if you’re not taking a blood thinner. The mutation in itself is not a reason to avoid donating blood, but you should not give blood if you are using an anticoagulant (blood thinner). Check with your provider.
You should either contact your provider or go to the nearest Emergency Room if you think you’re having a deep vein thrombosis. If you have symptoms of a pulmonary embolism, you should go to the closest emergency room.
If you are already taking an anticoagulant, make sure you keep regular appointments with your provider.
A note from Cleveland Clinic
A prothrombin gene mutation can raise your risk of getting a pulmonary embolism or deep venous thrombosis. You may never get a dangerous clot, but it’s helpful to know the warning signs in case you do. Talk to your provider to see if you should be taking a blood thinner. Keep going to your follow-up appointments with your provider, especially if you’re taking a blood thinner.
Last reviewed by a Cleveland Clinic medical professional on 09/28/2021.
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