The exact cause of celiac disease is unknown. There is evidence that the disorder is inherited since it tends to run in families. The disorder may be caused by an abnormal immune response to proteins found in grains, particularly gluten and the related protein gliadin.

The intestines contain projections (called villi) that normally absorb nutrients. Celiac disease causes these villi to become flattened and lose the ability to absorb nutrients. Weight loss, anemia, and vitamin deficiencies may occur as a result of this malabsorption (inadequate absorption of nutrients from the intestinal tract).

Symptoms appear in babies within 6 months of introducing food containing gluten into the diet. The disease also affects children and adults. As many as 1 in 250 people may have celiac disease and some studies estimate that it is even more common, at 1 in 150. Most people with the disease do not know they have it, as only about 1 in 2,500 is diagnosed.

Risk factors are a genetic or familial tendency toward the disease. The disorder is most common in Caucasians and those with Northern and Southern European ancestry. Approximately 70% of reported cases occur in women.

Diseases that can be associated with celiac disease include lactose intolerance, dermatitis herpetiformis (a burning, itching, blistering rash), insulin-dependent diabetes mellitus (IDDM), systemic lupus erythematosus, thyroid disease, and autoimmune disorders.