About one in six people of African ancestry carries a small change in a gene called CD36. According to a Cleveland Clinic-led study published in JAMA on October 19, 2026, that single variant accounts for roughly 9% of dilated cardiomyopathy in this population. That is more than the share attributed to TTN, the gene genetic laboratories have long treated as the most common inherited cause.
It is not on the panels most US hospitals order.
“The genetic contributor that matters most to this condition in this population is one that hospitals across the country are not testing for,” Krishna Aragam, director of cardiovascular genomics and precision medicine at Cleveland Clinic and the study’s senior author, said in a Cleveland Clinic news release. He described the situation as a current gap in clinical genetic testing rather than a future implication.
Below is what the study found about CD36 heart failure risk, what the gene actually does in heart muscle, why a variant this common stayed off standard tests, and what the results cannot tell you. That last part matters most. A 9% population figure is not a personal risk estimate, and nothing here means a carrier is destined for heart failure.
What the Study Actually Found
Dilated cardiomyopathy is the most common form of cardiomyopathy. The left ventricle stretches and weakens, so it pumps less blood with each beat, and the condition is a leading reason people eventually need a heart transplant. It clusters in families more strongly among people of African ancestry than among people of European ancestry, a pattern that known genes had never fully explained.
The researchers pooled genetic and clinical data from four US cohorts: the All of Us Research Program, the Million Veteran Program, the Penn Medicine Biobank, and the DCM Precision Medicine Study. Together the datasets included 82,623 people of predominantly African ancestry, with a mean age of 53.4 years.
They compared three groups of variants: the CD36 Y325* nonsense variant (zero, one, or two copies), truncating variants in TTN, and pathogenic or likely pathogenic variants in 11 other high-confidence dilated cardiomyopathy genes.
Among the 1,316 people in the analysis who had dilated cardiomyopathy, the pattern was clear:
- People with two copies of the CD36 variant had 4.8 times the odds of dilated cardiomyopathy compared with noncarriers (95% CI, 3.1 to 7.3).
- People with one copy had 1.4 times the odds (95% CI, 1.2 to 1.7).
- TTN truncating variants carried the highest per-carrier risk in the study, at 8.5 times the odds (95% CI, 5.5 to 13.0).
Per-carrier risk is not the same as population impact, though. Only 33 of those cases (2.5%) were homozygous for CD36, against 56 (4.3%) with a TTN truncating variant and 16 (1.2%) with a pathogenic variant in one of the other 11 genes.
Once carrier frequency is folded in, the ranking flips. The CD36 variant’s population attributable fraction came out at 9.0%, made up of 6.2% from people with one copy and 2.8% from people with two. The figure for TTN truncating variants was 3.7%.
A note on the case count. The JAMA abstract reports 1,316 cases of dilated cardiomyopathy. The Cleveland Clinic news release states 1,625, a number that matches the earlier preprint version of the analysis. This article uses the published JAMA figures throughout.
What CD36 Does in the Heart
CD36 is a protein that sits in the membrane of heart muscle cells and pulls long-chain fatty acids out of the bloodstream and into the cell. In cardiac tissue that job is not incidental. The healthy adult heart normally gets 50 to 70 percent of its ATP, the cell’s energy currency, from fatty acid oxidation, according to a review of myocardial fatty acid metabolism in Physiological Reviews.
Most inherited forms of dilated cardiomyopathy damage the heart’s contractile machinery directly. Sarcomere proteins that generate force are built wrong, and the pump fails from the inside out.
The CD36 variant works earlier in fuel supply. When Y325* truncates the protein, the transporter is lost from the cell surface. Fatty acid uptake falls, the muscle leans more heavily on glucose, and the resulting energy shortfall eventually shows up as a weakened, thinning, dilated ventricle. That mechanism was described in the Nature Genetics study that first linked the variant to dilated cardiomyopathy in 2025.
The biological distinction has clinical consequences. A defect in fuel handling is a different kind of target than a broken sarcomere, and it may interact differently with the conventional drivers of heart failure, including high blood pressure, diabetes, and chronic kidney disease. CD36 has also been studied for decades in cardiovascular disease for its roles in atherosclerosis and platelet biology, which is one reason the cardiomyopathy finding arrived so late: the gene was already famous for something else.
There is an evolutionary reason the variant is so common in the first place. CD36 is a receptor that malaria parasites use to anchor themselves to blood vessels, and losing it appears to have offered some protection against severe malaria. The Nature Genetics authors note that positive selection in malaria-endemic regions of sub-Saharan Africa may have kept the variant circulating despite its cost to the heart, much as sickle cell trait persists for the same reason.
Why “9% of Cases” Is Not a 9% Risk
The 9% figure is a population attributable fraction. It estimates how much of the dilated cardiomyopathy burden in a population would not occur if the variant were absent, assuming the association is causal and the statistical model is sound. It describes a population. It says nothing about what will happen to one person.
Two things follow from that distinction. First, the number combines both carrier states, because one-copy carriers are numerous and two-copy carriers are rare. Second, a high population attributable fraction can come from a common variant with a modest effect just as easily as from a rare variant with a large one. CD36 is the first kind. TTN is the second.
[interactive_chart]{“type”:”bar”,”themeMode”:”light”,”background”:”#ffffff”,”title”:”Population attributable fraction of dilated cardiomyopathy”,”subtitle”:”Share of cases among people of African ancestry linked to each variant”,”source”:”JAMA, October 2026″,”sourceUrl”:”https://jamanetwork.com/journals/jama/fullarticle/10.1001/jama.2026.18449″,”unitSuffix”:”%”,”dataLabels”:true,”height”:380,”categories”:[“CD36 Y325*, one copy”,”TTN truncating variants”,”CD36 Y325*, two copies”],”series”:[{“name”:”Population attributable fraction”,”data”:[6.2,3.7,2.8]}],”colors”:[“#b91c1c”,”#0f766e”,”#f59e0b”],”xAxis”:{“min”:0,”max”:8,”tickAmount”:4}}[/interactive_chart]
That is why both claims in the study’s conclusion can be true at the same time. TTN variants carry more risk for the individual who has one. CD36 accounts for more disease across the whole population, because so many more people carry it.
The same dilution applies to the obvious worry produced by a 9% headline. Some readers will hear “9% of carriers get sick.” Those are different fractions. The 9% is a slice of the disease burden, not a personal risk, and it is built from two groups with very different odds.
One Copy, Two Copies, and What Carrier Status Means
Roughly 16% of African-ancestry participants carried one copy of CD36 Y325* and about 0.77% carried two. Those frequencies are what turn a small odds ratio into a large population number, and copy number is the most useful piece of information a carrier can obtain.
| Measure | One copy | Two copies |
|---|---|---|
| Share of African-ancestry participants | About 16% | About 0.77% |
| Odds ratio for dilated cardiomyopathy | 1.4 (95% CI, 1.2 to 1.7) | 4.8 (95% CI, 3.1 to 7.3) |
| Share of the 1,316 cases | Not separately reported | 2.5% (33 people) |
| Population attributable fraction | 6.2% | 2.8% |
Neither column is a diagnosis, and the gap between them cuts both ways. An odds ratio of 1.4 describes a modest shift in risk across millions of people. Most of those people will never be diagnosed with dilated cardiomyopathy.
Even for the higher-risk genotype, the arithmetic is sobering: 33 homozygous carriers appear among 1,316 cases, which means the other 1,283 cases involved people who did not have two copies.
That is what incomplete penetrance looks like in real data. A variant can raise risk substantially and still leave most carriers unaffected over a lifetime, because dilated cardiomyopathy usually requires other contributors as well. With TTN truncating variants, cardiologists have documented that a second hit such as alcohol exposure, pregnancy, chemotherapy, or another genetic factor often precedes disease. The CD36 study did not measure those interactions, but there is no biological reason to assume this variant behaves differently.
Why the Variant Is Missing From Standard Panels
The natural question is why a variant with this much population impact was never added to routine testing. Start with the panels themselves, because the omission is easy to verify.
Mayo Clinic Laboratories’ 63-gene dilated cardiomyopathy panel does not list CD36. Neither does its 83-gene comprehensive cardiomyopathy panel, nor the 44-gene dilated cardiomyopathy panel offered by Oregon Health & Science University. The curated gene list matters more than any single lab menu: the Heart Failure Association of the ESC consensus statement on genetic counselling in dilated cardiomyopathy names 19 genes with high evidence for routine clinical testing. CD36 is not among them.
Four reasons explain the gap, and none of them is simple oversight.
- Panels are built for rare variants. Clinical variant classification was designed around alleles that are absent or vanishingly rare in population databases, and common risk alleles traditionally live in risk scores rather than diagnostic panels. A variant carried by roughly one in six people, with an odds ratio of 1.4 per copy, does not resemble a classic monogenic cause.
- Reference data is heavily European. The variant is virtually absent in people of European ancestry. In genomic databases dominated by European-ancestry samples, a variant that is common in West African populations either does not appear or appears as a handful of entries, which makes its true frequency easy to misjudge. A 2026 review of next-generation sequencing in dilated cardiomyopathy makes the broader point directly: pathogenic variants are less often classified in African-ancestry cohorts, largely because ancestry-specific reference data is missing.
- Gene lists are curated, short, and slow. Diagnostic panels are not built from the whole genome. They are built from evidence-graded lists reviewed by committees, and those lists update on multi-year cycles. The first solid link between this variant and dilated cardiomyopathy was published in 2025.
- A common variant creates a reporting problem. Telling one in six patients that they carry a variant which moderately raises their odds, with no specific treatment attached, is a genuinely difficult result to return. Laboratories worry, reasonably, about anxiety and cascading tests with no management plan behind them.
That last point is not a bureaucratic excuse, and it points at the real limitation of the study. The research shows that the variant matters. It does not show that knowing about it changes what happens to a patient.
What the Study Cannot Tell You
The paper is a genetic association study, and several questions sit outside what it can answer.
- Lifetime absolute risk. Odds ratios compare groups. They do not tell an individual carrier what their chance of developing dilated cardiomyopathy actually is, which requires long-term follow-up of people who were healthy at baseline.
- Whether carriers need different monitoring. Nothing in the data supports a specific surveillance schedule for carriers who have normal heart function today.
- Whether to test people without disease. Aragam’s argument is narrower than universal screening: include the variant in the genetic evaluation of dilated cardiomyopathy in people of African ancestry. That is diagnostic testing for people who already have the condition or a strong family history, not population screening of healthy adults.
- Cause and effect. The analysis compares people with and without dilated cardiomyopathy at a point in time. That design is powerful for measuring association and weaker for establishing that the variant causes disease in every carrier.
- Whether the numbers transfer to everyone. The cohorts lean older and male, with 47,124 men among the 82,623 participants and a large contribution from the Million Veteran Program. Estimates from that population may not map neatly onto younger adults or onto women.
- What ancestry means for one person. The study uses genetic ancestry, which is a measure of shared inheritance and not the same thing as self-identified race. Clinical decisions should not be driven by how a patient checks a box on a form.
What to Ask a Clinician If You Carry the Variant
If you have dilated cardiomyopathy, a family history of it, or a genetic report that happens to mention CD36, these questions tend to produce useful answers.
- Was CD36 actually on the panel? Ask for the gene list, not the test name. A negative report from 2024 may mean the variant was never examined in the first place.
- Do I have one copy or two? The difference between the two risk estimates is roughly a factor of three, and it is the most relevant number on the report.
- What does this mean alongside my family history, imaging, and other risk factors? A genotype is one input. Blood pressure, diabetes, kidney function, and echocardiographic findings all carry weight.
- Should my relatives be tested? Once a variant is confirmed in a family, first-degree relatives can usually be tested for that single change rather than a full panel, which is cheaper and far easier to interpret.
- Does anything about my care change? Today the honest answer is often no, because no trial has tested a CD36-guided treatment strategy. A clinician who says so is being accurate rather than dismissive.
- Can I speak with a genetic counselor? Pre-test and post-test counseling is recommended in cardiomyopathy guidelines precisely because results like this one are statistical rather than binary.
What Would Have to Change
Cleveland Clinic says it plans to add the CD36 variant to its own cardiomyopathy genetic testing. Wider adoption would need more than one health system’s decision, and three gaps stand out.
- Absolute risk estimates. Prospective cohorts that follow carriers who were healthy at enrollment would convert odds ratios into the numbers patients actually ask about.
- Evidence that the result changes management. Panels tend to absorb variants once a result alters surveillance, family screening, or treatment. Right now the case rests on diagnostic yield and family cascade testing rather than on therapy.
- Guideline and payment review. Commercial panels follow professional guidance and insurance coverage, and both move slowly.
The therapeutic gap is not unique to CD36. Anyone who progresses to advanced heart failure still faces a short list of options: medication, implanted devices, and transplant, with experimental regenerative approaches still working through trials. A genetic result earns a permanent place on a panel when it routes someone toward one of those options sooner.
There is a fourth consideration that has nothing to do with molecular biology. A variant added to a panel only helps people who are offered the test. Access to broad genetic sequencing remains uneven, and the patients most likely to carry this variant are not necessarily the ones most likely to reach a cardiomyopathy genetics clinic. Fixing the panel without fixing the referral pathway would leave most of the gap in place.
Frequently Asked Questions
What percentage of people of African ancestry carry the CD36 variant?
About 16% carry one copy and about 0.77% carry two, according to the JAMA study. Cleveland Clinic describes total carriage as approximately 17%. The variant is virtually absent in people of European ancestry, which is why it went unrecognized in cardiomyopathy genetics for so long.
Does carrying CD36 Y325* mean I will develop heart failure?
No. Most carriers never develop dilated cardiomyopathy. One copy raises the odds modestly, and even two copies leave the large majority of people unaffected. The variant is best understood as one contributor to risk among several, not as a predetermined outcome.
Is CD36 deficiency the same thing as the CD36 Y325* variant?
They overlap without being identical. CD36 deficiency is a laboratory finding, meaning the protein is missing or reduced on the surface of platelets and monocytes, and it is a well-known issue in transfusion medicine because CD36-negative patients can develop antibodies after transfusion or pregnancy. The Y325* variant is one genetic route to losing the protein, and people with two copies would be expected to show that loss. Much of the older CD36 literature uses the deficiency label rather than a specific variant name, which is part of why the cardiac connection surfaced late.
Is CD36 heart failure hereditary?
The variant is inherited, but it does not behave like a single-gene disease. Dilated cardiomyopathy clusters in families more strongly among people of African ancestry, and CD36 explains part of that clustering rather than all of it. The rest involves other genes, environmental exposures, and conditions such as high blood pressure and diabetes.
Why is CD36 not on standard cardiomyopathy panels?
Because panels are built around rare, high-penetrance variants and short curated gene lists, and a variant carried by roughly one in six people does not fit that framework. European-skewed reference databases and the multi-year lag between discovery and panel revision compound the problem.
The Bottom Line
This study does not say that carriers are destined for heart failure, and it does not recommend screening everyone. It says something narrower and considerably more useful: among people of African ancestry, a variant that most US laboratories do not test for now accounts for more dilated cardiomyopathy than any gene they do test for.
That is a gap in a test menu, not a verdict about anyone’s heart. Closing it requires a laboratory decision, a guideline review, and evidence about absolute risk that does not exist yet. The practical takeaway for patients is smaller and more immediate: if you have had genetic testing for cardiomyopathy, ask which genes were on the list. If CD36 was not there, a negative result is incomplete.
