Coeliac disease is caused by a reaction to gliadin, a prolamin (gluten protein) found in wheat, and similar proteins found in the crops of the tribe Triticeae (which includes other common grains such as barley and rye). Upon exposure to gliadin, and specifically to three peptides found in prolamins, the enzyme tissue transglutaminase modifies the protein, and the immune system cross-reacts with the small-bowel tissue, causing an inflammatory reaction. That leads to a truncating of the villi lining the small intestine (called villous atrophy).
Severe coeliac disease leads to the characteristic symptoms of pale, loose, and greasy stool (steatorrhoea) and weight loss or failure to gain weight (in young children). People with milder coeliac disease may have symptoms that are much more subtle and occur in organs other than the bowel itself. It is also possible to have coeliac disease without any symptoms whatsoever. Many adults with subtle disease only have fatigue or anaemia
If the person is already eating a gluten-free diet. Intestinal damage begins to heal within weeks of gluten being removed from the diet, and antibody levels decline over months. For those who have already started on a gluten-free diet, it may be necessary to perform a rechallenge with some gluten-containing food in one meal a day over 6 weeks before repeating the investigations
From September 2003 to August 2004, at the Fundação Pró-Sangue Blood Center of São Paulo, São Paulo, Brazil, 4,000 serum samples obtained from blood donors of both genders aged 18 to 65 years (median, 31 years), regardless of gender, were processed. The only inclusion criterion for the study was that donors had to have a fixed residence for at least two years in the city of São Paulo. Individuals with known CD were excluded from participation.