When a person with celiac disease eats any of these grains, a protein called gluten found in them causes a reaction in their immune system. The immune system damages the tiny, fingerlike projections, called villi, that line the small intestine. Villi are important because nutrients pass through them into the bloodstream. When villi are destroyed, the person becomes malnourished, no matter how much food they eat. The person has trouble absorbing carbohydrates, fat, protein, fat-soluble vitamins, calcium, magnesium, iron, folate, and zinc.

Celiac is likely caused by both genetic factors (meaning it runs in families) and a trigger, which is gluten. It is an autoimmune disease. The disease can develop in children and in adults. But it's unclear who will develop it and when. Some research suggests that the risk for celiac disease may be reduced if a baby is introduced to gluten while being breast-fed.

This form of sprue is found in some tropical areas, such as the Caribbean, India, and Southeast Asia. Experts aren't sure of the exact cause, but they suspect some kind of infection, including all of those listed (bacteria, viruses, parasites, or contaminated food), or conditions such as vitamin deficiency. The main symptoms of tropical sprue are diarrhea, weight loss, and anemia. Treatment often is a course of antibiotics. Tropical sprue is rare, but celiac sprue is common.

All of the diseases listed are autoimmune diseases, as is celiac disease. Other autoimmune diseases that may occur along with celiac disease include dermatitis herpetiformis, collagen vascular disease, and Sjogren's syndrome. Experts suspect that the link between celiac disease and these other autoimmune diseases is genetic.

Symptoms of celiac disease include weight loss, diarrhea, excessive gas, behavior changes, delayed growth (in children), failure to thrive (in infants), bone or joint pain, seizures, tingling numbness in the legs, tooth discoloration, and infertility. Symptoms differ from person to person. Some people have only belly (abdominal) symptoms. Others have no symptoms. People without symptoms still have undamaged parts of their small intestine that are able to absorb enough nutrients. These people are still at risk for complications.

A person with celiac disease has higher than normal levels of certain antibodies. These antibodies can be measured with a blood test. If symptoms and the blood test suggest celiac disease, the healthcare provider may then order a biopsy of the small intestine. The biopsy checks for damage to the villi. Without these tests, celiac disease is hard to diagnose. That's because its symptoms are a lot like those of irritable bowel syndrome, Crohn's disease, ulcerative colitis, diverticulosis, chronic fatigue syndrome, and depression.

A person with celiac disease must pass up any foods that contain gluten. For most people, a gluten-free diet will stop symptoms, heal intestinal damage, and prevent further damage. The healing process can take from 6 months (children) to 2 years (adults). This special diet must be followed for the rest of the person's life, because eating any amount of gluten can damage the small intestine. Some people with celiac disease have a small intestine so damaged by the disease that it can't heal even with a change in diet.

These foods don't contain wheat gluten and so are safe to eat. In addition, flours made from these foods and corn grains are available for baking and cooking. Gluten-free products are also available. Other foods that are safe to eat include plain meat, fish, fruits, and vegetables. Should a person with celiac disease eat oats? Eating uncontaminated oats is fine. But oats can be contaminated with gluten. Check with your healthcare provider or dietitian before trying oats. Commercial food products may contain gluten in the form of additives, preservatives, and stabilizers. This can also apply to nonfood items such as medicines and mouthwash. Even vitamins and probiotics can contain gluten. Meet with a dietitian to discuss safe food choices.

Lymphoma, which is cancer of the lymph system, can develop in the small intestine of a person with celiac disease. Because it may be hard for a person with celiac disease to absorb enough calcium, osteoporosis may develop. Because of poor absorption of nutrients, a woman with celiac disease who is pregnant may be at risk for miscarriage, as well as neural tube defects and other congenital defects. Seizures may be caused by poor absorption of folate. Poor absorption of folate and iron may cause anemia.