Is celiac disease genetic?
A curious adult from Alabama asks:
"My twin granddaughters were recently diagnosed with celiac disease (an intolerance to wheat). They say this runs in families. Is it genetic and should we all be tested for this disease?"
Editor’s note (8/14/2021): While there is still no genetic test that can say for certain whether or not you will develop celiac disease, there are now genetic tests that can rule out whether or not you have the disease. You can read more about genetic testing and celiac disease here.
You're right; celiac disease does run in families. And when something runs in the family, genes are often involved. However, there is no genetic test that can tell for certain whether or not you will develop celiac disease.
I can't really give advice on whether or not you and your family should be tested. What I can do is tell you what is and isn't known about celiac disease so you can make an informed decision.
Testing for Celiac Disease
As you might guess from the previous discussion, there is a test available to figure out whether you have celiac disease. But it isn't a genetic test.
Usually a doctor can't just look at your symptoms and tell you that you have celiac disease. The symptoms are too similar to lots of other diseases.
Luckily there is a simple blood test that can tell you whether or not you have the disease.
The blood test looks for certain antibodies. As you might already know, antibodies are used by the body to fight infections. The antibodies doctors are looking for attack something called gluten and, in addition, the small intestine.
Gluten is found in wheat and barley. The body thinks this gluten is something like a bacteria or virus and attacks it with antibodies. In the process, the antibodies also attack the small intestine. (The small intestine is where gluten is digested.)
This is why the symptoms of celiac disease appear when these folks eat wheat. The damage to the small intestine means they can't digest their food properly. They don't get enough nutrients and suffer from malnourishment, gas, bloating and diarrhea.
When people with celiac disease stop eating wheat, the antibodies stop attacking and the small intestine heals. Soon, the symptoms disappear.
So there is a very sensitive test out there for figuring out if you have celiac disease. But because the test isn't genetic, it can't tell someone the odds of passing the disease on to their children.
Genetic testing and Celiac Disease
Some genetic tests can tell whether you are a carrier for certain diseases. A carrier doesn't have any symptoms but can pass the disease gene on to their kids. Diseases like hemophilia, color blindness and brittle bone disease are examples where tests like this are available.
But the test for celiac can't tell you that; it can only tell you whether or not you have the disease. And a genetic test is a long way off.
The reason a genetic test isn't happening anytime soon is that scientists don't know which genes to test. Of course, that doesn't mean some progress isn't being made. Even though scientists don't know the exact genes involved in celiac disease, they have begun to narrow them down to a group of genes.1
Just having these genes isn't enough to get celiac disease, though. Of the 30-40% of Caucasians who carry these genes, only 3% will get the disease.1,2 When this happens it is possible that environmental factors may play a role.
So is there any reason for someone with no symptoms to take the test? Maybe.
Celiac disease affects at least 1 out of every 133 Americans.1 And yet, many people with the disease don't show any symptoms until their 40's or 50's.
These people without symptoms, though, can suffer from some of the same issues that people with symptoms deal with, particularly malnutrition. The celiac test can find these asymptomatic people so they can avoid these problems by avoiding wheat.
So, there you have it. It is up to you whether or not you want to be tested, given all of this information.
Author: Eric Churchill
When this answer was published in 2005, Eric was a postdoctoral fellow in the Department of Molecular Pharmacology, studying proteomic approaches to the treatment of cardiovascular disease in Daria Mochly-Rosen’s laboratory. Eric wrote this answer while participating in the Stanford at The Tech program.