Not so long ago, celiac disease was considered to be an allergy to gluten, a protein found in wheat and other grains, that predominantly affected children.

Now, however, it is known that celiac disease is an autoimmune disease that affects about 1 percent of people in the United States, says Dr. Alessio Fasano, director of the Center for Celiac Research at the University of Maryland School of Medicine.

What is celiac disease?

Nowadays, celiac disease is perceived to be an autoimmune disease like diabetes and multiple sclerosis, not a food allergy to wheat as thought before.

When people who are genetically skewed toward the disease eat wheat, they, first of all, have a reaction [to wheat] in the intestine. The reaction makes the intestine leakier so that more wheat comes into the body. Then the immune cells of the intestine will mount an inflammatory response that ultimately will damage the liner cells [of the intestine] that are charged with absorbing nutrition. Ultimately, it can lead to further damage throughout the body.

Who is susceptible to this disease?

We thought it was extremely rare. Now we know it is the most frequent human gene disorder.

One out of 133 people in the United States is affected with celiac disease. Celiac disease occurs in 5 [percent] to 15 percent of the offspring and siblings of a person with celiac disease. ... It is strongly suggested that family members be tested, even if they are asymptomatic.

What causes it?

Like all autoimmune diseases, its recipe is the genes you are born with. We know some of the genes involved. And there is a trigger - something in the environment that is mismanaged by the people who have this disease. But this means that this is the only autoimmune disease that we know the trigger for: the protein - gluten - found in wheat, barley and rye.

What are its symptoms?

When the celiac disease was first described, we were under the impression that this was a disease affecting only kids and would only present GI [gastrointestinal] symptoms - mainly diarrhea, weight loss and stunted growth.

Over time, we have come to appreciate the complexity of the clinical symptoms, which can affect any system or organ of the body.

So not only can it affect people of any age, but it can include the GI symptoms - vomiting, nausea, irritable bowel symptoms, constipation instead of diarrhea - and many others.

How is it diagnosed?

The other strength of the condition [in addition to knowing what triggers this disease] is that we have a very, very good screening test. There is a blood test for specific antibodies unique to celiac disease and if you test positive for these, you have a 95 percent chance of having celiac disease.

How is it treated?

Well, the luxury of celiac disease, compared to all other autoimmune diseases, is that we know the trigger. Knowing the trigger - gluten - is the cornerstone of how you treat the disease. We can't remove the genes - we aren't quite there yet - but we can completely avoid for life products that contain gluten. Now that is easy to say but very, very complicated to do.

Once gluten has been removed from the diet, are the symptoms alleviated?

It depends. In the vast majority of cases, they will completely go away: Anemia will be resolved and with it, fatigue, and so on.

But the issue is different if you have had the symptoms for so long that they cannot be fixed anymore. For example, if you are diagnosed ... by around age 30, then osteoporosis can be fixed. But after that, it cannot be changed. Or if you are diagnosed before puberty, then you can catch up in your growth, but after that you really can't do anything.

What do you tell your patients who are diagnosed with celiac disease?

The vast majority who are diagnosed with this disease react with anger, dismay and frustration. Especially teenagers, because if you think [about] what this implies, you understand their frustration: From this moment on, you can't eat pasta, pizza, bagels, cookies, cakes, beer.

It means your lifestyle changes. When you travel, socialize, go to college, it affects your lifestyle and will limit it in certain ways.

I tell them, "I do understand your feelings, but let's say I have the power to trade your celiac disease for any other autoimmune disease, which you would rather have? Cancer, diabetes, Crohn's, cystic fibrosis?" They say, "Well, I will keep the celiac disease."