The small intestine is responsible for absorbing food and nutrients. Thus, damage to the lining, such as occurs in celiac disease, results in impaired absorption of nutrients, a condition referred to as "malabsorption." The associated signs and symptoms vary from person to person. In the mildest form, which doctors sometimes refer to as "subclinical," patients may have no symptoms whatsoever. However, such patients may have evidence of malabsorption on laboratory testing, such as a low blood count from decreased absorption of iron. Others may have diarrhea, weight loss, abdominal discomfort, excessive gas, osteoporosis, and other signs and symptoms due to deficiencies of specific vitamins and nutrients. Still others may have signs or symptoms of a number of conditions that are more common in patients with celiac disease, including:

• Dermatitis herpetiformis (an intensely itchy blistering skin condition mostly on the arms, legs, and torso)
• Diabetes mellitus
• Thyroid problems (usually an underactive thyroid [ie, hypothyroidism])
• Depression, fatigue, and other neurologic diseases
• Arthritis
• Liver disease

WHAT CAUSES IT? — As mentioned above, celiac disease is caused by an abnormal immune system response to dietary gluten. Why some people develop the abnormal response and others do not is incompletely understood. Genetic factors are clearly important since celiac disease occurs primarily in whites of northern European ancestry. There is a strong link between inheritance of specific genes that regulate the immune response (HLA DQ2) and risk for celiac disease. The exact mechanisms that underlie the abnormal immune system response are gradually being uncovered.

HOW IS IT DIAGNOSED? — Celiac disease may be suspected in patients who have clinical or laboratory abnormalities suggesting the diagnosis. Blood tests detecting certain antibodies produced by patients with celiac disease can strongly support the diagnosis. The most accurate of these tests are for:

• IgA endomysial ("end-oh-MEE-see-al") antibody (IgA EMA)
• IgA tissue transglutaminase ("trans-GLOOT-a-min-ace") antibody (IgA tTG)

These tests are positive in more than 90 percent of people with untreated celiac disease, and are rarely positive in those without celiac disease.

Confirmation of the diagnosis requires examination of a sample of the lining of the small intestine under the microscope. This is usually accomplished during an upper endoscopy, which is a very safe test that involves swallowing a small flexible instrument that can allow your doctor to examine the upper part of the gastrointestinal system. A sample of the small intestine (biopsy) can be obtained during the examination. The biopsy is not painful.

The most characteristic finding of the small intestinal lining under the microscope is flattening of the finger- or frond-like structures, which are called "villi" (show histology). Villi are essential for the normal absorption of nutrients. Once gluten is removed from the diet, the villi grow back. Some doctors recommend documenting the regrowth by repeating a biopsy some months after gluten has been eliminated from the diet. In some cases, if the diagnosis is still in doubt after a period of treatment with a gluten free diet it may be necessary to reintroduce gluten and demonstrate that the flattening returns. A decline in the levels of endomysial antibody in the blood are expected once on a gluten-free diet.

Patients with celiac disease should be tested for nutritional deficiencies that may result from malabsorption. Common tests include a blood count to detect anemia from iron, folic acid, or vitamin B12 deficiency, and tests to detect calcium or vitamin K deficiency. Many doctors recommend that patients with celiac disease undergo specific testing for bone loss. One method involves using a DEXA (dual energy x-ray absorptiometry) scan, a painless imaging test that determines the density of bone. Those who have developed significant bone loss may require specific treatment. Vaccination against pneumonia (Pneumovax) has also been recommended.

HOW IS IT TREATED? — The cornerstone of treating celiac disease is to completely eliminate gluten from the diet. Patients who are malnourished because of the disease may also need certain nutrient supplements. As mentioned above, those who have developed significant bone loss may require specific treatment.

Maintaining a gluten-free diet can be a difficult task requiring major lifestyle adjustments since gluten is contained in the most commonly consumed grains in the Western world (wheat, rye, and barley) and is included as an additive in multiple prepared foods. Thus, it is usually best to consult with a nutritionist who can provide detailed guidance and written information on permissible foods. In addition, a number of helpful resources are available that can provide dietary advice and support. ().

Fortunately, life on a gluten free-diet has become increasingly easier with the gaining popularity of gluten-free foods. Excellent gluten-free substitutes for traditional gluten-containing foods are now widely available.

DO I HAVE TO BE STRICT ABOUT ELIMINATING GLUTEN? — People with celiac disease should be very strict about avoiding gluten since even small amounts can cause the disease. Oats do not appear to be harmful but should be avoided unless special steps have been taken during their production to avoid contamination by the other harmful cereals.

People who had no symptoms when diagnosed often find it particularly difficult to accept a gluten-free diet. Indeed, some doctors have questioned the need for a strict gluten-free diet in such people given the lifestyle restrictions that such a diet can pose. However, several lines of evidence would support adhering to a gluten-free diet even in those without symptoms:

• Despite feeling clinically well, such patients may have a variety of deficiencies in specific vitamins or nutrients that may ultimately cause symptoms (such as anemia due to iron deficiency or bone loss due to vitamin D deficiency).
• Untreated celiac disease has been associated with an increased risk of certain types of cancer. Although unproven, it is reasonable to assume that the risk might be reduced by a gluten-free diet even in those who have no symptoms.
• The likelihood that patients with celiac disease will develop other immune-related disorders (such as diabetes mellitus and thyroid disease) may be related to the duration of exposure to gluten.
• Pregnant women with untreated celiac disease are at increased risk for having low birth weight newborns.

WHAT IS THE PROGNOSIS? — The majority of patients completely respond to a gluten-free diet and go on to lead a normal life. Approximately 70 percent of those with symptoms at diagnosis notice an improvement in intestinal symptoms (such as diarrhea) within two weeks of beginning a gluten-free diet; in others, the response is more gradual. The skin lesions present in some patients with celiac disease (dermatitis herpetiformis) may take several months to resolve. The response to some of the other associated conditions is variable.

The most common reason for failure to respond is inadvertent ingestion of gluten-containing foods. However, other disorders mimicking celiac disease should be considered in those who continue to have symptoms despite a gluten-free diet.

Are there possible complications? — In addition to anemia, bone loss, and other consequences of malabsorption, a very small percentage of patients develop intestinal symptoms that do not respond to a gluten-free diet, a condition called "refractory sprue." Some patients with refractory sprue have a condition known as "ulcerative jejunitis" in which the small intestine develops multiple ulcers that do not heal. Treatment involves medications designed to suppress the immune system. Cancer of the lymph system (lymphoma) is also an uncommon but recognized complication of long-standing celiac disease. Other types of cancers may also be more common in people with untreated celiac disease than the general population, although the actual risk is very low.

IMPLICATIONS FOR YOUR FAMILY — Your family will need to adjust to your new diet. Thus, it may be helpful for them to share in your education about celiac disease.

Another issue related to your family is that the risk of celiac disease is increased in the relatives of those with celiac disease. Thus, first-degree relatives (a parent, brother, sister, or child) of a person who has been diagnosed with celiac disease should consider being screened for the disease, which is typically accomplished with blood antibody testing as described above. You should discuss these issues with your doctor.