Your cholesterol panel looks fine, your blood pressure is normal, and yet heart disease still runs in your family, or shows up earlier than it should. Standard bloodwork captures a lot, but it doesn’t capture everything, and genetics is part of the reason why, alongside factors like inflammation and clotting tendency that don’t show up on a typical lipid panel. One striking example is a region of chromosome 9 known as 9p21, one of the most consistently replicated genetic findings in cardiovascular research. Its association with coronary artery disease has been shown to be independent of cholesterol levels, blood pressure, obesity, and diabetes across multiple large genome-wide studies (Holdt et al., 2010). This is one contributing factor among several, not something that overrides the value of standard cardiovascular screening.
9p21: A Major Risk Factor With No Clear Mechanism
The 9p21 locus was one of the earliest and most striking discoveries of the genome-wide association study era, identified independently by two research groups in 2007 and since replicated across European, Korean, and Japanese populations, with a large meta-analysis estimating about a 27% increase in relative risk per risk allele (Assimes & Roberts, 2016).
Why This One Is Genuinely Unusual
Unlike most cardiovascular risk genes, this region doesn’t contain a protein-coding gene at all. It sits near two cell-cycle regulator genes, CDKN2A and CDKN2B, and overlaps a long non-coding RNA called ANRIL, whose exact role in atherosclerosis is still being worked out more than a decade after the locus was first discovered (Holdt et al., 2010). Research suggests it may influence vascular smooth muscle cell behavior and cell cycle regulation within arterial plaques, but a definitive mechanism remains elusive.
A Risk That Depends on Context
Interestingly, one study found that the 9p21 risk variant was associated with cardiovascular events specifically in people who already had detectable coronary artery calcification, but not in those without it (Wang et al., 2014). This suggests the genetic risk may need a certain amount of existing arterial changes to become clinically meaningful, another layer of nuance beyond what a single blood test could reveal.
LPA and a Cholesterol Particle Standard Panels Don’t Measure
Lipoprotein(a), or Lp(a), is an LDL-like particle attached to a distinct protein called apolipoprotein(a), and its blood levels are almost entirely determined by genetics rather than diet or lifestyle. Crucially, Lp(a) isn’t included in a standard lipid panel, which typically measures only total cholesterol, LDL, HDL, and triglycerides.
Mendelian randomization studies, a method that uses genetic variants to test for causal relationships, support Lp(a) as a causal contributor to atherosclerotic cardiovascular disease, distinct from and additive to LDL cholesterol risk (Reyes-Soffer et al., 2025). Current guidelines now recommend measuring Lp(a) at least once in a person’s lifetime given how much it’s determined by genetics rather than modifiable factors (Bielecka-Dabrowa et al., 2024). A large UK Biobank study did find that a genetic risk score for Lp(a) performed comparably to direct measurement, but didn’t add meaningfully more predictive information beyond simply measuring Lp(a) directly (Trinder et al., 2021), a useful reminder that in this case, a specific blood test may be just as informative as genetic testing itself.
Factor V Leiden and Clotting Tendency
Factor V Leiden is a genetic variant that makes blood resistant to one of the body’s natural anticoagulant controls, raising clotting risk. It’s fairly common, affecting an estimated 5% of white Americans of European descent, though it’s markedly rarer in Asian, African, and Indigenous Australian populations (Kujovich, 2024).
It’s worth being direct about where the evidence is strong and where it isn’t. Factor V Leiden’s role in venous conditions like deep vein thrombosis and pulmonary embolism is well established, but its contribution to arterial disease, including heart attack and typical stroke, is genuinely controversial, with the overall evidence suggesting it isn’t a major independent driver of arterial clots on its own (Kujovich, 2011). That said, the same source notes that carrying this variant alongside traditional cardiovascular risk factors was associated with an approximately elevenfold increase in stroke risk, suggesting its real-world danger may lie mostly in combination with other risks rather than as a standalone factor.
What Standard Screening Still Does Well
None of this diminishes the value of routine cholesterol panels, blood pressure checks, and blood glucose testing, which remain the backbone of cardiovascular risk assessment for the vast majority of people. These genetic factors are best understood as filling in gaps for a smaller subset of people whose family history or personal risk doesn’t line up with otherwise normal-looking bloodwork, not as a replacement for standard preventive care.
Where Genetic Testing Fits In
If heart disease runs in your family despite normal-looking bloodwork, a cardiovascular disease genetic report can walk through markers like these in personalized detail. It’s meant to add context for a conversation with your doctor, not to replace standard cardiovascular screening or a direct Lp(a) blood test where clinically indicated.
Frequently Asked Questions
Should everyone get their Lp(a) tested?
Many current guidelines recommend at least a one-time Lp(a) measurement for adults, given how strongly it’s determined by genetics rather than lifestyle. Ask your doctor whether this makes sense for your situation.
If I carry the 9p21 risk variant, does that mean I’ll develop heart disease?
No. It increases relative risk modestly and may interact with other factors like existing arterial calcification, but it doesn’t determine outcomes on its own.
Does Factor V Leiden mean I’m at high risk for a heart attack?
Not necessarily on its own. Its clearest, best-established risk is for venous clots like DVT and pulmonary embolism. Its role in arterial events like heart attacks is less clear and appears to depend heavily on other coexisting risk factors.
