Three Genes for Blood Clots

Numerous factors increase a person’s risk for developing blood clots in deep veins, a condition known medically as venous thromboembolism (VTE). VTE starts with the formation of a blood clot deep in the body, usually in the legs, and occasionally escalates into a more serious condition called “pulmonary embolism” if the clot breaks free and travels to the lungs. About one in 100 people with European ancestry will develop a blood clot in his or her lifetime and in nearly 25% percent of these cases the first sign will be sudden death.Fracturing your hip or leg, having hip or knee replacement surgery, being immobilized like on a long flight, being pregnant, smoking, and taking oral birth control pills all increase risk for VTE to varying degrees. Genetics also plays a role and a new study by lead author John Heit from the Mayo Clinic suggests that variants of just three genes – F5, F2, and ABO – account for nearly all the possible genetic risk in people with European ancestry. These results imply that researchers are unlikely to discover new genetic factors that significantly impact VTE risk in the general population.Two of the three major genes have especially large impacts on risk for VTE. The F5 gene encodes the factor V clotting factor, a protein that causes blood cells to stick together. People with one copy of the risky version of this gene (T at ) have a condition called “Factor V Leiden”, named after the city in the Netherlands where the role of this variant was first discovered, and are about five times more likely to develop VTE than people without the T version. The F2 gene encodes prothrombin, another clotting factor, and individuals with one risky version of this gene (A at i3002432) are nearly four times more likely to develop a blood clot compared to people without the A version. The risky versions of F5 and F2 are fairly rare in the general population.

23andMe customers can view their results for Venous Thromboembolism in their account. Not yet a customer? Visit our store!
The ABO gene determines the common blood groups O, A, B and AB. It’s been shown that people with non-O blood types are at increased risk for VTE and a number of variants in or near the ABO gene have been associated with VTE risk. The study by Heit further confirms that the version of the ABO gene that makes someone have a non-O blood type also makes him or her about two times more likely to develop VTE.(23andMe reports on a SNP in the ABO gene – – that is highly correlated with another SNP that defines the O blood group. People with at least one C at typically have a non-O blood type and are at increased risk for VTE.)In addition to showing that versions of F5, F2 and ABO account for most risk in people with European ancestry, the study also suggested that a variant of the SELP gene further increases a person’s risk for VTE but only if he or she also inherited the risky version of F5 from the same parent. The SELP gene encodes a protein called P-Selectin and it’s already known that increased levels of P-Selectin are linked to VTE. But since less than 5% of the population even has the risky version of F5, this new finding only explains risk for a small number of people.23andMe updated it’s VTE Established Research report in March of 2012 and currently reports on variants of the F5, F2, and ABO genes. Our report is thus very comprehensive for people with European ancestry. For reasons that are still unclear, VTE is much more common in people with European and African-American ancestry and less prevalent in Asian and Latino populations. More research is needed to define the genetic risk factors in non-European populations.
Editor’s note: Pending an FDA decision, 23andMe no longer offers new customers access to health reports referred to in this post. Customers who purchased prior to November 22, 2013 will still be able to see their health reports, but those who purchased after that time will not. Those customers will have access to ancestry information as well as access to their uninterpreted raw data.
  • Very informative article! It’s great to know these facts because so many suffer blood clots and usually suddenly

  • Paradigm

    My doctor prescribed this test for me because my mother, grandmother, and sister all had significant medical histories that involved blood clots. I was unique in my family for never having had a problem, so I was confident that I hadn’t inherited the family affliction. I was flabbergasted with the results. The test I took was an earlier version that lacked the refinement of the ABO, but it uncovered a cluster of several genetic markers, rare in the aggregate: one F5, a double F2, non-O blood, and protein C resistance.

    The results were shocking to me and my doctor, but decades have gone by and I have remained clot-free. My lifestyle has not been safer than that of my afflicted relatives; for example, not knowing that I was at risk, I used birth control pills, smoked, had my babies at home, and used hormone treatment. My relatives did none of these things yet they were repeatedly hospitalized starting in early adulthood, one dying very young of a blood clot in the heart. In contrast, here I am at 61, never having experienced the slightest blood clot.

    No one has any idea why the family genes were harmful to them and not to me. If your results come back positive, don’t be talked into blood thinners and living in fear. Genes are not the whole story; no one seems to know why they sometimes trigger and sometimes don’t. I am walking testimony that one can sail through life with every one of these blood clotting genes and a risky lifestyle to boot.

  • DC

    I was pregnant when first diagnosed with blood clots, it (they started in my legs). I initially began on shots of blood thinner (Lovenox) due to my pregancy. I was told I could possibly only have to take it 3 addt’l months after my child’s birth. Didn’t happen! Going through numerous tests, visit to an oncologist 12 years later I am still on a thinner (coumidin) generic warfin.

    I have always been concerned (scared) due to the clotting alone if not treated can result in death, but what is even more terrifying is the number of years I’ve been on this drug. My mother died of a heart attach in her sleep, the medical report is so detailed and medically challenging to me I don’t understand it and honestly I’m afraid to.

    I have a 12 year old and I know I have to get her tested to see if this is genetic. However, reading the article above confirms that fact indeed. It is a panic stricken thought to know that I could have a gene which increases a chance of me dying, possibly finding out my mother had it but even more scary if I found out my daughter has it.

    I have no insurance and the tests are expensive. I know I have to get this done!

    Thank you for the article.

    • BethannH

      Hello DC,
      I’m really sorry to hear about your history with blood clots. The 23andMe test is $99 and includes results for the three genetic variants discussed in this article. If you buy more than one kit, the second is 20% off. I wish you the best.

  • Hello,

    I have Factor V Leiden and have had a stroke and heart attack. I was 38 when it started. I did loose a baby when I was 28, I am now 44. As far as i know, ALL my kids have it. My daughter almost lost my grandson when she was pregnant. They say my son has one of the worse cases thev’e seen. My 16 year old has had a clott in the heart. Look, how bad is this thing? i mean, some doctors say don’t worry its fine. What do you think??? I am supposed to take Plavix, but cant always afford it. Just don’t know what to think. 🙁

    • BethannH

      Hello Joanne,
      I’m very sorry to hear about your and your family’s heart problems. People with Factor V Leiden are predicted to be five times more likely to develop a blood clot. This is a significant risk. We recommend that people with this genetic variant discuss their concerns with their physician as blood clots can be fatal.
      I hope this helps. Bethann