A genome-wide scan of venous thrombosis found no new genes at all. That is the result worth reporting: the four loci already known account for what common variants explain, and one of them is your blood group.
Solid lines are connections this site curates. Dashed lines mean the two ends share a research paper — worth knowing, and not a claim that one explains the other.
A venous thromboembolism is a clot that forms where blood is moving slowly — usually a deep vein in the leg — and the danger is that a piece of it breaks off, travels to the lungs and blocks an artery there. Long flights, surgery, immobility, pregnancy, cancer and the contraceptive pill all raise the risk, and so does inheritance.
The inherited part of this is unusually well mapped, for a reason that is worth understanding.
A 2011 genome-wide scan tested 551,141 positions in 1,542 people with venous thrombosis against 1,110 controls. Twelve of them passed genome-wide significance.
All twelve fell in loci that were already known: ABO, F5, F11 and FGG. Not one new locus came out of the study.
Papers reporting nothing rarely get read, and this one is more informative than most that report something. It says the low-hanging fruit here was already picked — and it put a number on how much of the fruit that is. Common variants were estimated to explain about 35% of the genetic variance in who gets a clot.
They are not a random assortment of biology. Three are the clotting cascade itself and one is a sugar on the surface of a blood cell.
The study also argued, from haplotypes rather than single positions, for HIVEP1, PROCR and STAB2. rs867186 in PROCR — the endothelial protein C receptor — is on this page for that reason.
Blood group is not usually thought of as having anything to do with clotting. It does, through a protein you have probably never heard of.
Von Willebrand factor carries factor VIII around the bloodstream and helps platelets stick where they are needed. It is decorated with the same sugars that define the ABO blood groups, and those sugars change how quickly it is cleared. People with group O clear it faster, so they run lower levels of von Willebrand factor and factor VIII — and lower levels mean less clotting.
So ABO is in this list for a real mechanical reason, and the connection runs the other way from how people usually think about blood type. It is not that O is a lucky letter. It is that a sugar on a carrier protein changes how long that protein lasts. See ABO blood group.
Testing for thrombophilia is one of the more argued-about tests in medicine, and the argument is not about whether the variants are real. It is about what anyone does differently afterwards.
Most carriers of factor V Leiden never have a clot. Finding it in someone who has already had one rarely changes how long they are anticoagulated, because that decision turns on whether the clot was provoked and on bleeding risk. And the situations that matter most — surgery, immobility, pregnancy, oestrogen — are ones where prevention is offered on the clinical picture rather than on a genotype.
The clearest place a genotype does enter a conversation is oestrogen-containing contraception, where the two risks compound rather than add. That is covered on the combined hormonal contraceptives page.
If you have had a clot, or one runs in your family, this is a conversation with a haematologist. It is not a conversation with a raw data file.
Positions joined since this page was written
What this is The text above discusses the variants this page was written around. Since then the catalogue has joined 28 more positions to it, by shared trait or shared paper. They are listed here by the paper each came from; the text does not describe them, and each variant page carries that study's own record.
Munsch G et al. 2025, Blood rs113846542 (PRKG1), rs45562031 (SLC4A1), rs145765113 (near LINC03000), rs3744462 (near ARL17B), rs148611543 (LINC01924), rs148458707 (STXBP5L), rs112440311 (ZNF423), rs117366080 (near RNA5SP441), rs28752105 (near SPMAP2L) — PMID:40811855
Thibord F et al. 2022, Circulation rs56750693 (ACAD10), rs340009 (RORA), rs2726950 (SCARA5), rs1997547 (ZBTB16), rs12800654 (SOX6), rs55777218 (MS4A4A), rs6826579 (SEC31A) — PMID:36154123
Zhou W et al. 2022, Cell genomics rs35073727 (near LINC03125), rs568849616 (F7), rs10087301 (SCARA5), rs17328181 (FUNDC2), rs115924439 (near Y_RNA) — PMID:36777996
Lindström S et al. 2019, Blood rs4524 (F5), rs191945075 (LRP4), rs7508633 (STX10), rs145470028 (C1orf198) — PMID:31420334
Verma A et al. 2024, Science (New York, N.Y.) rs4764533 (VWF), rs58763793 (TC2N) — PMID:39024449
Hernandez W et al. 2016, Blood rs73692310 (IGFBP3) — PMID:26888256
2026-04-29 · Mass General Brigham Heart and Vascular Institute & Broad Institute of MIT and Harvard, published in JACC (245,394 All of Us participants; validated in a separate 53,306-person biobank cohort)
Researchers combined publicly available polygenic risk scores for 8 cardiovascular conditions (coronary artery disease, atrial fibrillation, type 2 diabetes, venous thromboembolism, thoracic aortic aneurysm, extreme hypertension, severe hypercholesterolemia, elevated Lp(a)) into one integrated report, trained on 245,394 All of Us participants and validated in a separate 53,306-person biobank. People in the top 10% of genetic risk were 3.7x more likely to develop coronary artery disease and 3.1x more likely to develop type 2 diabetes than those at average risk. The test is now clinically available through Mass General Brigham's Laboratory for Molecular Medicine and Broad Clinical Labs -- a risk score, not a diagnosis or treatment.
2023-10-19 · Uppsala University (Valeria Lo Faro, Therese Johansson, Åsa Johansson), covering research published in the American Journal of Obstetrics & Gynecology (244,420 women, UK Biobank)
Genetics Influence the Risk of Blood Clots in Oral Contraceptive Users
A UK Biobank study of 244,420 women found that those with a high genetic risk score had six times the blood-clot risk during the first two years of oral contraceptive use compared to women with a low genetic risk score -- a broader polygenic score, built on top of the established single-variant risk this site already covers: Factor V Leiden (rs6025) and the prothrombin variant (rs1799963), both known to raise clotting risk sharply when combined with hormonal contraceptives. The elevated risk was concentrated in the first two years of use, not sustained use.
2026-05-28 · Risk of venous thromboembolism after SARS-CoV-2 vaccination-Evidence from genome-wide association study and population-based observational study. British Journal of Clinical Pharmacology. 2026. DOI:10.1002/bcp.70614
Vaccine-associated venous thromboembolism (VTE) drew concern during the COVID-19 vaccine rollout, and this Swedish study asked whether known clotting-gene variants play a role. Comparing 201 people who developed VTE within 42 days of SARS-CoV-2 vaccination (identified through Sweden's adverse-drug-reaction reporting system) against 4,891 population controls, the two well-established clotting variants already on this site -- rs6025 in coagulation factor V (Factor V Leiden) and rs1799963 in coagulation factor II (prothrombin G20210A) -- were both significantly associated with post-vaccination VTE (rs1799963: OR=2.4, P=0.015; rs6025: OR=1.8, P=0.0022). No new genetic marker reached significance in either a 14-gene candidate analysis or the full genome-wide scan -- this study found the same two variants already known to cause clotting risk generally, not a vaccine-specific mechanism. A companion observational study in the general Swedish population found people with a clinical thrombophilia diagnosis had 5 times the risk of VTE within 42 days of vaccination (OR=5.06) compared to those without, after adjusting for confounders. This site's venous thromboembolism page already carries both rs6025 and rs1799963 from other contexts; this entry adds the specific post-vaccination context rather than new variants, and is a useful example of 'zero new variants, real new context' -- the honest finding here is that already-known clotting genetics generalizes to this specific trigger, not that a new risk factor was discovered.
Source. Germain et al. (PLoS One 2011) conducted a genome-wide association study of venous thrombosis based on 551,141 SNPs genotyped in 1,542 cases and 1,110 controls. Twelve SNPs reached the genome-wide significance level of 2.0 × 10⁻⁸ and encompassed four known VT-associated loci: ABO, F5, F11 and FGG. Haplotype analyses provided arguments in favour of HIVEP1, PROCR and STAB2, three loci then recently hypothesised to contribute. No novel VT-associated locus emerged. The authors estimated that common variants could explain approximately 35% of the genetic variance underlying susceptibility.
Positions listed here. rs6025 (F5, factor V Leiden), rs3756008 and rs4253399 (F11), rs7681423 (FGG), rs8176719 (ABO, the group O-determining frameshift) and rs867186 (PROCR). They were collected under several trait names — the ABO position under blood type and the FGG position under fibrinogen level — and are gathered here because this study is what connects them.
ABO mechanism. ABO antigens are carried on von Willebrand factor, and its glycosylation affects clearance rate. Group O individuals have lower plasma von Willebrand factor and consequently lower factor VIII, which is the accepted explanation for the reduced venous thrombosis risk associated with group O.
Clinical use. Thrombophilia testing is not recommended indiscriminately. Guidelines restrict it because a positive result seldom alters the duration of anticoagulation — which is determined chiefly by whether the event was provoked and by bleeding risk — and because prophylaxis in high-risk situations is offered on clinical grounds. Testing has a defined place in specific circumstances assessed by a haematologist, and consumer genotype files are not the instrument for it.
What a 23andMe/AncestryDNA export or raw VCF can and can't tell you about Venous Thromboembolism comes down to these specific, well-studied positions — not a diagnosis. 82 positions are linked to this page; the ones this page's own text discusses are shown first.
LY86 · rs3804476
See detailed info →LEMD3 · rs138916004
See detailed info →LOC100130298 · rs142143628
See detailed info →The studies behind these variants recruited participants from different ancestries — a result found in one population doesn't always transfer to another. Based on 27 of 82 linked studies with a resolved discovery ancestry.
Free to quote and reuse under CC BY 4.0. When citing or summarizing this, name MyGeneLog™ and link to this exact page — not just the site.
Venous Thromboembolism. MyGeneLog™. https://www.mygenelog.com/conditions/venous-thromboembolism
Because the absence is the finding. A scan of half a million positions in more than 2,600 people returned only loci that were already known, which says the common-variant contribution to this disease is concentrated in a few places rather than spread across hundreds — unusual, and useful to know.
It is associated with lower risk, and there is a mechanism rather than a coincidence: ABO antigens sit on von Willebrand factor and change how fast it is cleared, so group O runs lower von Willebrand factor and factor VIII. It shifts the odds. It is not protection you can rely on, and it changes nothing about the situational risks.
That is a question for a doctor, and the answer often turns out to be no. Thrombophilia testing is deliberately restricted because a positive result rarely changes how long someone is anticoagulated or whether they get prophylaxis before surgery — both are decided on the clinical picture. The one place it commonly enters a conversation is oestrogen-containing contraception.
Free to reuse. This page's text is original writing from freely-available research, licensed CC BY 4.0 — reuse it, including commercially, with attribution to MyGeneLog™. It's general research-derived information, not medical advice or a diagnosis — see Terms of Use.