an inherited autoimmune digestive disorder in which people cannot tolerate gluten, a protein constituent of wheat, barley, malt, and rye flours. General symptoms of the disease include the passage of foul, pale-coloured stools (steatorrhea), progressive malnutrition, diarrhea, decreased appetite and weight loss, multiple vitamin deficiencies, stunting of growth, abdominal pain, skin rash, and defects in tooth enamel. Advanced disease may be characterized by anemia, osteoporosis, vision disturbances, or amenorrhea (absence of menstruation in women).

The way in which the disease manifests varies widely. For example, some people experience severe gastrointestinal symptoms, whereas others are asymptomatic, are irritable and depressed, or develop an itchy skin rash with blisters, known as dermatitis herpetiformis. If left undiagnosed or uncontrolled, celiac disease may lead to intestinal adenocarcinoma (malignant tumour of glandular tissue) or intestinal lymphoma or to miscarriage in pregnant (pregnancy) women. Pregnant women affected by the disease and thus suffering from vitamin deficiencies are also at an increased risk for giving birth to infants with congenital disorders (congenital disorder).

In children (childhood disease and disorder), celiac disease begins within several months of adding gluten-containing foods such as cereal to the diet. However, the onset of the disease is also influenced by the length of time the child was breast-fed and by the amount of gluten that the child ingests. The disease frequently is first noticed following an infection and is chronic, with periods of intestinal upset, diarrhea, and failure to grow and gain weight, interspersed with periods of apparent normality. Adult celiac disease commonly begins past the age of 30, but it may appear at an earlier age following severe stress, surgery, or childbirth.

Several gene mutations have been identified in celiac disease; however, genetic mutations themselves do not give rise to the disease. Instead, it is triggered by the combination of genetic and environmental factors; i.e., when a genetically predisposed individual eats foods containing gluten. In people with celiac disease, gluten stimulates the immune system to produce autoantibodies (autoantibody) that damage the mucosal (mucous membrane) lining of the small intestine.

In most cases, celiac disease can be diagnosed (diagnosis) by blood tests for anti-tissue transglutaminase antibody and anti-endomysial antibody. Diagnosis is usually confirmed by endoscopic examination and biopsy of the small intestine. endoscopy provides visual evidence of intestinal damage, marked by flattening of the villi (villus) in the mucosal lining, which normally project into the intestinal cavity and increase the surface area available for nutrient absorption. Biopsied tissue is examined for the presence of certain lymphocytes (lymphocyte) that indicate inflammation caused by gluten.

Celiac disease is estimated to occur, on average, in about 1 in every 266 people worldwide; however, only about three percent of these people are actually diagnosed with celiac disease. This is in part because some people are asymptomatic, but it is also attributed to misdiagnosis, since many symptoms of the disease are similar to other conditions, including irritable bowel syndrome, Crohn disease, and chronic fatigue syndrome. Several autoimmune diseases have mutations in the same chromosomal region as celiac disease, and although the underlying mechanisms remain unclear, these diseases often develop in association with celiac disease. As a result, the longer a person with celiac disease remains undiagnosed or misdiagnosed, the more likely they are to develop an associated autoimmune disease, such as a thyroid (thyroid gland) disorder, type I diabetes (diabetes mellitus), or autoimmune hepatitis.

The symptoms of most patients are relieved by strict adherence to a gluten-free diet. In children the intestinal mucosa is usually healed within several months to one year of initiating the diet, and in adults, it is usually healed within two years. In rare cases, symptoms and destruction of the mucosal lining may progress despite a gluten-free diet; these individuals generally receive intravenous vitamin therapy.