Why did you get celiac disease, and not your brother or sister? Why does one of your children have it, but another doesn’t?
If you are reading about how celiac disease gets started, or a doctor is trying to explain it to you, there is an as yet unexplained step. Something allows pieces of gluten (gliadin) to get through the lining of the small intestine. Once these pieces pass through the lining, they get to the place where they start a cascade of reactions that results in the symptoms of celiac disease. But how do those first pieces get through?
This is important because those pieces of wheat or gluten are not any problem when they stay in the intestine. They don’t trigger CD until they get through what may be a leaky intestinal wall.
There is no definite answer to the question of how they get in. It may be something to do with the intestinal lining of people with celiac disease that doesn’t keep out pieces of gluten the way the intestines of people without celiac disease do. Or there may be some event, something that happens to a person that allows the protein pieces into where they start causing trouble.
Many researchers believe that for susceptible children who have celiac disease in the family, the “stomach flu,” which is the common term for gastroenteritis, is the event that starts the disease. Getting one of these viruses in early childhood may make the lining of the small intestine leaky. There is a particular group of virus suspected, called rotaviruses.
So, while the lining is leaky, pieces of gluten cross through and trigger what eventually becomes celiac disease. For this to happen, the child has to have the genes to predispose him or her to celiac disease. The fact that you may need both the genes and some kind of extra exposure would explain why only around 11% of children who have a parent with celiac disease also have it. If it was just genetic, more children would have CD.
There is also the question of when this might happen. Would it need to happen when the child first ate wheat products, or does the timing not matter?
When scientists want to answer a question like this, the best kind of studies are what are called “prospective, randomized, controlled trials.” This means you take two similar groups of people and expose one group to whatever is thought to cause a disease or treat a disease, and not expose the other group. If there is a difference, it is more certain that the factor studied this way may be causing the outcome. It is obviously not possible to take children from families with celiac disease and infect them with viruses at an early age to see what will happen.
Instead, research in this area involves looking for an association between early intestinal infections and later development of CD. One study in Sweden looked at a group of over nine thousand children that had been followed from infancy. Records, including diaries kept by parents, contained the needed information about the children, like how long they were breast fed and when they first ate wheat, as well as illnesses. Researchers compared a group of 44 children with celiac disease to other children similar in every other way. They found no association between early intestinal infection or any other infection at the time the children first ate gluten-containing food and future development of celiac disease.
The intestinal infections in this study were reported by parents; the viruses or other causes of the infections were not known. It was noted by the authors of the study that Swedish parents rarely take young children with minor illnesses to the doctor. It is not known how many of the children had rotavirus infection. Other studies have found a link between rotavirus infection and later development of celiac disease.
It is worth noting that there since 2006 there has been an effective, oral vaccine to protect infants and young children from rotaviruses. In the case of rotaviruses, 74% to 87% of all illness episodes can be prevented by vaccinations. If rotavirus infection is a possible CD trigger, there is a group of children now who may avoid that trigger. It will be years before any changes due to adopting the rotavirus vaccination schedule will be visible.
While this study did not provide an answer, it is a good example of how researchers are looking to try and find a celiac disease trigger. Future studies may actually find a more specific answer.