” Coeliac disease, also spelled celiac disease, is a long term autoimmune disorder primarily affecting the small intestine that occurs in people who are genetically predisposed. Classic symptoms include gastrointestinal problems such as chronic diarrhoea, abdominal distention, malabsorption, loss of appetite, and among children failure to grow normally. This often begins between six months and two years of age. Non-classic symptoms are more common, especially in people older than two years. There may be mild or absent gastrointestinal symptoms, a wide number of symptoms involving any part of the body, or no obvious symptoms. Coeliac disease was first described in childhood; however, it may develop at any age. It is associated with other autoimmune diseases, such as diabetes mellitus type 1 and thyroiditis, among others.
Coeliac disease is caused by a reaction to gluten, which are various proteins found in wheat and in other grains such as barley, and rye. Moderate quantities of oats, free of contamination with other gluten-containing grains, are usually tolerated. The occurrence of problems may depend on the variety of oat. Upon exposure to gluten, an abnormal immune response may lead to the production of several different autoantibodies that can affect a number of different organs. In the small-bowel this causes an inflammatory reaction and may produce shortening of the villi lining the small intestine (villous atrophy). This affects the absorption of nutrients, frequently leading to anaemia.
Diagnosis is typically made by a combination of blood antibody tests and intestinal biopsies, helped by specific genetic testing. Making the diagnosis is not always straightforward. Frequently, the autoantibodies in the blood are negative and many people have only minor intestinal changes with normal villi. People may have severe symptoms and be investigated for years before a diagnosis is achieved. Increasingly, the diagnosis is being made in people without symptomsas a result of screening. Evidence regarding the effects of screening, however, is not sufficient to determine its usefulness. While the disease is caused by a permanent intolerance to wheat proteins, it is not a form of wheat allergy.” https://en.wikipedia.org/wiki/Coeliac_disease