The destruction of the inner lining of the small intestine in celiac disease is caused by an immunological (allergic) reaction to gluten.
Gluten is a family of proteins present in wheat, barley, rye, and sometimes oats.
Individuals with celiac disease may develop diarrhea, steatorrhea, weight loss, flatulence, iron deficiency anemia, abnormal bleeding, or weakened bones. However, many adults with celiac disease may have either no symptoms or only vague abdominal discomfort such as bloating, abdominal distension, and excess gas.
Children with celiac disease may have stunted growth, and if untreated, childhood celiac disease can result in short stature as an adult.
Small intestinal biopsy is considered the most accurate test for celiac disease.
Blood tests can be performed to diagnose celiac disease; these include endomysial antibodies, anti-tissue transglutaminase antibodies, and anti-gliadin antibodies.
There is no cure for celiac disease. The treatment of celiac disease is a gluten free diet.
In most individuals, a gluten free diet will result in improvement in symptoms within weeks. Many individuals report symptom improvement within 48 hours.
In children with celiac disease, successful treatment with a gluten free diet can lead to the resumption in growth (with rapid catch up in height).
Failure to respond to a gluten free diet can be due to several reasons; the most common reason is failure to adhere to a strict gluten free diet.
Refractory celiac disease is a rare condition in which the symptoms of celiac disease (and the loss of villi) do not improve despite many months of a strict gluten free diet. It may progress to cancer.
The treatment of refractory celiac disease is first to make sure that all gluten is eliminated from the diet. If there still is no improvement, corticosteroids such as prednisone, and immunosuppressive agents (medications that suppress a person's immune system) such as azathioprine and cyclosporine may be used.
Adults with celiac disease have a several-fold higher than normal risk of developing lymphomas (cancers of the lymph glands) in the small intestine and elsewhere. They also have a high risk of small intestinal and, to a lesser degree, of esophageal carcinomas (cancers of the inner lining of the intestine and esophagus).
The prognosis of individuals with celiac disease who develop lymphoma, collagenous celiac disease, or jejunal ulcers is poor.
What is celiac disease?
Celiac disease is a disease of the small intestine. The small intestine is a 22 foot long tube that begins at the stomach and ends at the large intestine (colon). The first 10 inches (25cm) of the small intestine (the part that is attached to the stomach) is called the duodenum, the middle part is called the jejunum, and the last part (the part that is attached to the colon) is called the ileum. Food empties from the stomach into the small intestine where it is digested and absorbed into the body. While food is being digested and absorbed, it is transported by the small intestine to the colon. What enters the colon is primarily undigested food. In celiac disease, there is an immunological (allergic) reaction within the inner lining of the small intestine to proteins (gluten) that are present in wheat, rye, barley and, to a lesser extent, in oats. The immunological reaction causes inflammation that destroys the lining of the small intestine. This reduces the absorption of the dietary nutrients and can lead to symptoms and signs of nutritional, vitamin, and mineral deficiencies.
The other terms used forceliac disease include sprue, nontropical sprue, gluten enteropathy, and adult celiac disease. (Tropical sprue is another disease of the small intestine that occurs in tropical climates. Although tropical sprue may cause symptoms that are similar to celiac disease, the two diseases are not related.)
Celiac disease is common in European countries, particularly in Ireland, Italy, Sweden, and Austria. In Northern Ireland, for example, one in every 300 people has celiac disease. In Finland, the prevalence may be as high as one in every 100 persons. Celiac disease also occurs in North America where the prevalence has been estimated to be one in every 3000 people. Unfortunately, most population studies underestimate the prevalence of celiac disease because many individuals who develop celiac disease have few or no symptoms until later in life. Moreover, a study suggests that the prevalence of celiac disease in the United States is similar to that in Europe.
CELIAC DISEASE SYMPTOMS
Depending on the degree of malabsorption, the signs and symptoms of celiac disease vary among individuals, ranging from no symptoms, few or mild signs and symptoms, to many or severe signs and symptoms. There are two categories of signs and symptoms: 1) signs and symptoms due to malabsorption, and 2) signs and symptoms due to malnutrition including vitamin and mineral deficiencies.
1. Signs and symptoms due to malabsorption: Fat is the most commonly and severely affected nutrient in celiac disease. Gastrointestinal symptoms of fat malabsorption include:
- foul smelling gas,
- increased amount of fat in the stool, and
- abdominal bloating.
2. Signs and symptoms due to malnutrition including vitamin and mineral deficiencies include:
- weight loss,
- fluid retention,
- bruising easily,
- peripheral neuropathy,
- infertility, and
- muscle weakness.
How is celiac disease diagnosed?
Celiac disease is suspected when individuals have signs or symptoms of malabsorption or malnutrition. Other diseases, however, can produce malabsorption and malnutrition, for example, pancreatic insufficiency (when the pancreas is not able to produce digestive enzymes), Crohn's disease of the small intestine, and small intestinal overgrowth of bacteria. It is important, therefore, to confirm suspected celiac disease with appropriate testing.
Small intestinal biopsy
Small intestinal biopsy is considered the most accurate test for celiac disease. Small intestinal biopsies can be obtained by performing an esophagogastroduodenoscopy (EGD). During an EGD, the doctor inserts a long, flexible viewing endoscope through the mouth and into the duodenum. A long, flexible biopsy instrument is then passed through a small channel in the endoscope to obtain samples of the intestinal lining of the duodenum. Multiple samples usually are obtained to increase the accuracy of the diagnosis. A pathologist then can examine the biopsies (under a microscope) for the loss of villi and other characteristics of celiac disease such as increased numbers of lymphocytes.
Small intestinal biopsy does however, have some limitations. For example, acute viral gastroenteritis and allergy to cow's milk or soy protein can cause abnormal small intestinal biopsies that are indistinguishable from celiac disease. However, acute viral gastroenteritis is not easily confused with celiac disease because of the difference in the acuteness of symptoms. (Acute viral gastroenteritis has a sudden onset of symptoms and last only a few days.) It is however, easier to confuse cow's milk and soy protein allergies with celiac disease, but these allergic conditions are rare and primarily occur in young children. Despite these limitations, small intestinal biopsies are recommended even in individuals who have abnormal antibody tests for celiac disease. (See discussion that follows.)
Specific antibody tests for celiac disease
Antibodies are proteins that are produced by the immune system to fight viruses, bacteria, and other organisms that infect the body. Sometimes, however, the body produces antibodies against non-infectious substances in the environment (for example, hay fever) and even against its own tissues (autoimmunity).
Blood tests that are specific for celiac disease include antigliadin antibodies, endomysial antibodies, and anti-tissue transglutaminase antibodies. In patients with celiac disease, anti-gliadin antibody is produced against gliadin in the diet, and anti-tissue transglutaminase antibodies are antibodies produced against the body's own tissues.
Endomysial antibodies and anti-tissue transglutaminase antibodies are highly reliable in diagnosing celiac disease. An individual with an abnormal elevation of these antibodies has a greater than 95% chance of having celiac disease. Anti-gliadin antibodies are less reliable and have a high false positive rate. Thus a person with an abnormally elevated anti-gliadin antibody level does not necessarily have celiac disease. Nevertheless, anti-gliadin antibody levels are useful in monitoring the response to treatment because anti-gliadin antibody levels usually begin to fall within several months of successful treatment of celiac disease with a gluten free diet.
The newest test for celiac disease is a test for antibodies to parts of the gliadin molecule called deamidated gliadin peptides. This test appears to be as good for diagnosing celiac disease as antibodies to tissue transglutaminase. In fact, it has been speculated that if blood tests for antibodies to tissue transglutaminase and deamidated gliadin peptides are negative (that is, no antibodies are present) then celiac disease is virtually excluded, and perhaps there is no need for biopsies of the small intestine. Further studies will be needed, however, to prove this.
Who should undergo antibody blood tests for celiac disease?
Some experts recommend that antibody blood tests should be used to screen healthy persons with no signs or symptoms for celiac disease. In Italy, where celiac disease is common, all children are screened for celiac disease. Experts in the United States do not recommend screening healthy persons for celiac disease. Antibody blood tests are only recommended for individuals with a higher likelihood than normal of having celiac disease. These individuals are:
Individuals with chronic diarrhea (diarrhea that does not resolve in three weeks), increased amount of fat in the stool (steatorrhea), and weight loss
Individuals with excess gas, bloating, and abdominal distension
First and second degree relatives of individuals who have celiac disease
Children with growth retardation
Individuals with unexplained iron deficiency anemia
Individuals with skin rashes suggestive of dermatitis herpetiformis
Individuals with recurrent painful mouth sores (aphthous stomatitis)
Individuals with diseases known to be associated with celiac disease. Examples of these diseases include insulin-dependent diabetes mellitus, autoimmune thyroid disease, rheumatoid arthritis, systemic lupus, ulcerative colitis, etc.
Individuals with unexplained elevations of liver enzymes (AST or ALT) in the blood.
Why is it important to accurately diagnose celiac disease?
Diagnosis of celiac disease should be firmly established before commencing treatment with a gluten free diet for several reasons.
The gluten free diet is a life-long and tedious commitment that should not be taken lightly. It is more costly than a normal diet and has significant social implications, especially when dining out.
Individuals with irritable bowel syndrome (IBS) may experience improvement in bloating, abdominal pain, and diarrhea with a gluten free diet. These individuals may be misdiagnosed as having celiac disease. Without confirmation of celiac disease by small intestinal biopsy, they may be unnecessarily committed to life-long gluten restriction.
A gluten free diet can lower blood antibody levels and allows the microscopic appearance of the small intestine to lose the typical appearance of celiac disease, complicating subsequent efforts at making a firm diagnosis of celiac disease.
How are malabsorption and malnutrition evaluated in celiac disease?
Celiac disease causes malabsorption of nutrients and leads to malnutrition. Tests are available that help in the evaluation of malabsorption and malnutrition; however, because other diseases can cause both malabsorption and malnutrition, these tests cannot be used to diagnose celiac disease.
Stool examination for malabsorption
Fat in a sample of stool placed on a glass slide can be stained with a dye (Sudan stain) to make the fat visible under the microscope as globules. Stool from patients with celiac disease often contains many stained globules of fat, and Sudan staining is a quick and easy screening test for increased amounts of fat in the stool (steatorrhea). To conclusively diagnose steatorrhea, however, stool is collected over a 72-hour period, and the fat in the stool is chemically measured and quantified. Steatorrheic stools have abnormally high quantities of fat. Since malabsorption and steatorrhea can occur with other intestinal diseases (such as small intestinal bacteria overgrowth, small intestinal resection, extensive Crohn's disease of the small intestine, and chronic pancreatitis), stools with large amounts of fat only raises the suspicion of celiac disease but cannot be used to diagnose celiac disease.
Blood tests for malnutrition and vitamin deficiencies
Malabsorption reduces the absorption of protein and causes a reduction in blood protein levels. This can be seen commonly as a reduced blood level of albumin, the most concentrated protein in blood. Other proteins in blood, for example, transferrin also may be reduced.
Intestinal malabsorption can lead to deficiencies and low blood levels of iron, calcium, vitamin B12, folate, Vitamin D and vitamin K. These deficiencies, in turn, can lead to other blood test abnormalities such as:
Iron deficiency anemia: Iron is an important component of hemoglobin in red blood cells. When iron is deficient, the production of red blood cells is impaired, and anemia develops. Iron deficiency anemia can occur either through loss of blood (with its iron-containing red blood cells) or lack of intestinal iron absorption. Heavy menstrual bleeding and cancer of the colon that bleeds into the intestine are two common causes of iron deficiency anemia due to blood loss. Celiac disease causes iron deficiency anemia by reducing intestinal iron absorption. In fact, iron deficiency anemia can be an important clue to the presence of celiac disease.
Abnormally prolonged prothrombin time (ProTime): ProTime is a blood test that measures how quickly blood clots. Clotting of blood requires special proteins or clotting factors, many of which are made by the liver. Formation of clotting factors by the liver requires vitamin K. When vitamin K absorption from the intestine is reduced, as in celiac disease, the production of clotting factors by the liver is inadequate, and blood clotting is delayed. Delayed clotting is reflected in an abnormal ProTime, and individuals with an abnormal ProTime have a higher risk of abnormal or excessive bleeding.
Iron deficiency anemia, abnormal ProTime, steatorrhea, and low iron and vitamin levels can occur in diseases other than celiac disease. Therefore, the presence of these abnormalities only raises the suspicion of celiac disease but does not specifically diagnose celiac disease.
What is the treatment of celiac disease?
There is no cure for celiac disease. The treatment of celiac disease is a gluten free diet. Patients with celiac disease vary in their tolerance to gluten; some patients can ingest small amounts of gluten without developing symptoms while others experience massive diarrhea with only minute amounts of gluten. The standard treatment calls for complete avoidance of gluten for life. The principles of a gluten free diet include:
Avoid all foods made from wheat, rye, and barley. Examples are breads, cereals, pasta, crackers, cakes, pies, cookies, and gravies.
Avoid oats. Some individuals with celiac disease can tolerate oats in the diet. But long-term safety of oats in individuals with celiac disease is unknown. Also some oat preparations can be contaminated with wheat. Thus, it is probably best to avoid oats at least during the initial treatment with a gluten free diet. Once disease remission is achieved with a strict gluten free diet, small quantities of oats may be reintroduced into the diet under medical supervision.
Pay attention to processed foods that may contain gluten. Wheat flour is a common ingredient in many processed foods. Examples of foods that may contain gluten, to name only a few, include:
processed and canned meats,
Beware of tablets, capsules, and vitamin preparations that contain gluten. Wheat starch is commonly employed as a binding agent in tablets and capsules. Gluten also can be found in many vitamin products, and cosmetic products such as lipstick.
It is all right to drink wine, brandy, whiskey and other non-wheat or barley alcohol (in moderation!)
Avoid milk and other dairy products that contain lactose. Untreated individuals with celiac disease often are lactose intolerant. With successful treatment, dairy products can be reintroduced slowly into the diet.
It is alright to consume fish, fresh meats, rice, corn, soybean, potato, poultry, fruits, vegetables, and dairy products (for individuals who are not lactose intolerant)
Consult dietitians and national celiac disease societies for lists of gluten free foods. Read the food and product labels before buying or consuming any product. This is necessary because a manufacturer may change a product's ingredients at any time. A product that was gluten-free in the past may now contain gluten. Even branded products may be gluten free in one country but contain gluten in another country. If one is not certain after reading the labels, call the manufacturer.
Because individuals with severe malabsorption can develop vitamin and mineral deficiencies, vitamin and mineral supplements are important. All individuals should take a multivitamin daily. Individuals with iron deficiency anemia should be treated with iron. Individuals with anemia due to folate or B12 deficiency should be treated with folic acid and B12. Individuals with an abnormal ProTime should be treated with vitamin K. Individuals with low blood calcium levels or with osteoporosis should be treated with calcium and vitamin D supplements.
In most individuals, a gluten free diet will result in improvements in symptoms within weeks. Many individuals report symptom improvements within 48 hours. In children with celiac disease, the response to a gluten free diet can be dramatic. Not only will diarrhea and abdominal discomfort subside, but the child's behavior also improves, and growth resumes (with rapid catch up in height). These improvements in symptoms are followed by reappearance of intestinal villi. Complete normalization of the intestinal villi may take months. In many adult individuals, the improvement in symptoms is followed by only partial regeneration of intestinal villi. In individuals with dermatitis herpetiformis, the skin lesions also improve with a gluten free diet.
Many individuals with celiac disease may not understand the importance of life-long adherence to a gluten free diet. A study found that in patients diagnosed at least 20 years earlier with celiac disease, only half of the patients were following a strict gluten-free diet. The primary reason that patients followed the diet was to prevent symptoms-not to prevent complications. There was evidence of mild iron deficiency and abnormal bone density in one-third of the patients, suggesting that the lack of adherence to the diet was having health consequences.