Celiac disease has a strong genetic component. More than 99% of people with celiac disease carry specific immune system genes called HLA-DQ2 or HLA-DQ8, and having a first-degree relative with the condition gives you up to a 20% chance of developing it yourself. But genetics alone don’t seal the deal: most people who carry these genes never develop celiac disease.
The Two Genes Behind Celiac Disease
Two gene variants do the heavy lifting. HLA-DQ2 and HLA-DQ8 code for proteins on the surface of your immune cells. These proteins act like docking stations that present fragments of food to your immune system for inspection. In people with these variants, the proteins have an unusually strong grip on fragments of gluten, specifically after those fragments have been chemically modified by an enzyme in the gut lining. That modified gluten locks into the protein like a key in a lock, triggering an immune response that attacks the small intestine.
Roughly 18% to 30% of the general population carries HLA-DQ2 or HLA-DQ8. Yet only about 1% of people worldwide actually develop celiac disease. So carrying the genes is necessary but far from sufficient. Think of them as a loaded gun that still requires something to pull the trigger.
Risk for Family Members
If you have celiac disease, your parents, siblings, and children face meaningfully higher odds. Studies estimate that up to 20% of first-degree relatives are affected. Among those family members, 40% to 65% carry the HLA-DQ2 or HLA-DQ8 genes, roughly double the rate seen in the general population.
Twin studies make the genetic influence even clearer. When one identical twin has celiac disease, the other twin develops it about 75% of the time. For fraternal twins, who share only half their genes on average, that rate drops to about 11%. The gap between those two numbers tells researchers that genetics account for the majority of celiac disease risk, though the fact that 25% of identical twins don’t both develop it confirms that something beyond DNA is also involved.
Genes Beyond HLA
HLA-DQ2 and HLA-DQ8 are the biggest players, but they’re not the whole story. Since 2007, researchers have identified at least 40 additional gene regions linked to celiac disease. These non-HLA genes have much smaller individual effects. The HLA region increases risk by more than fivefold, while each non-HLA variant typically raises risk by 12% to 36%.
Some of these smaller-effect genes appear to influence when and how the disease develops. Certain variants seem to play a role in the early stages, when the immune system first starts producing antibodies against gluten, while others matter more in the later progression to full intestinal damage. This may help explain why celiac disease can appear at any age, from toddlerhood to the 60s and beyond, even in people who have been eating gluten their entire lives.
Environmental Triggers That Activate the Genes
Carrying the right genes sets the stage, but environmental factors often determine whether the disease actually switches on. Gluten exposure is obviously required, since it’s the protein the immune system reacts to. Beyond that, several triggers have been identified in large studies.
Childhood infections stand out. In the TEDDY study, which followed thousands of children over time, early gastrointestinal infections raised celiac risk by about 33%. Rotavirus infections showed a dose-response pattern: one infection nearly doubled the risk, and two infections increased it nearly fourfold. Respiratory syncytial virus (RSV) and seasonal influenza have also been linked to later celiac diagnosis, with risk increases of 46% and 26% respectively.
Breastfeeding duration may also matter. The same TEDDY study found that infants breastfed for fewer than four months had roughly double the risk of developing celiac disease compared to those breastfed longer. The theory is that breast milk may help shape the infant gut’s immune environment during a critical window.
What Genetic Testing Can Tell You
Genetic testing for celiac disease works differently from most medical tests. It’s far better at ruling the disease out than confirming it. If you test negative for both HLA-DQ2 and HLA-DQ8, your chance of having or ever developing celiac disease is essentially zero, with a negative predictive value approaching 100%. That result is reliable regardless of whether you’re currently eating gluten, which makes it useful in situations where other tests are harder to interpret.
A positive result, on the other hand, simply means you carry genes shared by up to 30% of the population. It tells you the disease is possible, not that you have it or will get it. For that reason, genetic testing isn’t used as a first-line screening tool. It’s most helpful in specific scenarios: when blood tests and biopsies give conflicting results, when someone has already been on a gluten-free diet before testing (which can cause standard antibody tests to come back falsely normal), or when family members of a diagnosed person want to know whether they even need ongoing monitoring.
For family members who test positive for the genes, periodic antibody screening every few years can catch the disease early if it does develop. Those who test negative can generally stop worrying about celiac disease altogether, even if a close relative has it.