celiac disease

celiac disease, an inherited autoimmune digestive disorder in which affected individuals 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).

Celiac disease is estimated to occur in 0.5 to 1.0 percent of people in Europe and the United States. Similar prevalence rates have been found in several other countries. Evidence suggests, however, that the prevalence of celiac disease can vary greatly by region. Moreover, only a small percentage of affected persons are actually diagnosed with celiac disease, suggesting that prevalence rates could be higher than estimated.

Manifestation of celiac disease

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 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.

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In children, 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.

Causes of celiac disease

Several gene mutations have been identified in celiac disease. However, genetic mutations by themselves do not give rise to the disease. Instead, it is thought to be triggered by a combination of genetic and environmental factors—i.e., when a genetically predisposed individual eats foods containing gluten. Environmental factors that are suspected of contributing to gluten intolerance include certain drugs, infections, and food additives. An additive known as microbial transglutaminase, which is used to help proteins adhere to one another to improve food texture, is a potential target for autoantibodies that damage the mucosal lining of the small intestine. Autoantibody production by the immune system is a hallmark of celiac disease. Moreover, the human body naturally produces a transglutaminase enzyme that is similar to microbial transglutaminase and is known to simulate the generation of autoantibodies.

Although about 90 peptides (protein fragments) in gluten have been found to cause some level of immune reaction, three fragments are notably toxic. One of these is found in certain gluten proteins in wheat, rye, and barley, and the other two are specific to wheat and rye glutens.

Diagnosis of celiac disease

In most cases, celiac disease can be diagnosed 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 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 that indicate inflammation caused by gluten.

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Underdiagnosis of celiac disease is partly due to the fact that 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 someone with celiac disease remains undiagnosed or misdiagnosed, the more likely that person is to develop an associated autoimmune disease, such as a thyroid disorder, type I diabetes, or autoimmune hepatitis.

Celiac disease management

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.