Coeliac disease ( ), also spelled celiac disease, is an autoimmune disorder of the small intestine that occurs in genetically predisposed people of all ages from middle infancy. Symptoms include chronic diarrhoea, failure to thrive (in children), and fatigue, but these may be absent and symptoms in all other organ systems have been described. It is estimated to affect about 1% of all Indo-European populations, but is thought to be significantly underdiagnosed. A growing portion of diagnoses are being made in asymptomatic persons as a result of increased screening.

Coeliac disease is caused by a reaction to gliadin, a gluten protein found in wheat (and similar proteins of the tribe Triticeae which includes other cultivars such as barley and rye). Upon exposure to gliadin, the enzyme tissue transglutaminase modifies the protein, and the immune system cross-reacts with the bowel tissue, causing an inflammatory reaction. That leads to flattening of the lining of the small intestine (called villous atrophy). This interferes with the absorption of nutrients because the intestinal villi are responsible for absorption. The only effective treatment is a lifelong gluten-free diet. While the disease is caused by a reaction to wheat proteins, it is not the same as wheat allergy.

This condition has several other names, including: cœliac disease (with "œ" ligature), c(o)eliac sprue, non-tropical sprue, endemic sprue, gluten enteropathy or gluten-sensitive enteropathy, and gluten intolerance. The term coeliac derives from the Greek κοιλιακός (koiliakόs, abdominal), and was introduced in the 19th century in a translation of what is generally regarded as an ancient Greek description of the disease by Aretaeus of Cappadocia. See also Google Books entry

Signs and symptoms

Classic symptoms of coeliac disease include diarrhea, weight loss (or stunted growth in children), and fatigue, but while coeliac disease is primarily a bowel disease, bowel symptoms may also be limited or even absent. Some patients are diagnosed with symptoms related to the decreased absorption of nutrients or with various symptoms which, although statistically linked, have no clear relationship with the malfunctioning bowel. Given this wide range of possible symptoms, the classic triad is no longer a requirement for diagnosis.

Children between 9 and 24 months tend to present with bowel symptoms and growth problems shortly after first exposure to gluten-containing products. Older children may have more malabsorption-related problems and psychosocial problems, while adults generally have malabsorptive problems. Many adults with subtle disease only have fatigue or anaemia.