Coeliac disease

Coeliac disease (also called celiac disease, non-tropical sprue, c(o)eliac sprue and gluten intolerance) is an autoimmune disorder characterised by damage to all or part of the villi lining the small intestine. This damage is caused by exposure to gluten and related proteins found in wheat, rye, malt and barley, and to a lesser degree in oats. Damage to the villi reduces the ability of the intestines to absorb nutrients, and it is believed that the resulting nutritional deficiencies likely cause the wide spectrum of symptoms associated with the disorder. Coeliac disease may lead to digestive problems frequently resembling irritable bowel syndrome, unexplained weight loss or other signs of nutritional deficiency due to malabsorption, and a wide range of other problems in different bodily systems, including the nervous system, the heart, and the teeth and bones. Coeliacs (people with coeliac disease) may also be symptom-free, but regardless of the presence or absence of symptoms, the disorder is associated with an increased risk of osteoporosis and intestinal cancer. Susceptibility to coeliac disease is genetic and many cases are diagnosed in childhood, but the disease can be triggered by environmental factors at any point in life.

The only treatment is a life-long gluten-free diet. No medications are required, and none have proven useful; trials with immunosuppressive medicines (to control the bowel inflammation) have been largely unsuccessful. Therefore, coeliacs do not need any medication; the disease can be controlled by strict adherence to a gluten-free diet, which allows the intestines to heal and resolves all symptoms in the vast majority of cases and, depending on how soon the diet is begun, can also eliminate the heightened risk of osteoporosis and intestinal cancer.

Contents

1 Signs and symptoms

2 Diagnosis

2.1 Tests
2.2 Biopsy appearance

7.1 Lifelong diet
7.2 Catholic Church

8 See also

9 Footnotes

Signs and symptoms

Strict adherence to a gluten-free diet typically resolves all symptoms and conditions caused by coeliac disease. In coeliacs who are not on a gluten-free diet, the disease may present through one or more of the following symptoms. The presence of these symptoms does not mean the individual is coeliac. These symptoms are also associated with other diseases, some of which are life-threatening; therefore, patients with these symptoms should promptly consult a doctor for differential diagnosis.

Dietary deficiencies, which may manifest as symptoms in particular body systems (e.g., digestive or nervous system) or may be noticed on routine blood tests, are common in coeliacs. Up to 50% of coeliac disease patients have malabsorption-related diarrhea (with bulky, pale, offensive-smelling stools which may float in the toilet bowl). This symptom is known as steatorrhea. However, some coeliacs suffer from constipation. Excess flatulence is common, and some coeliacs also experience infrequent, minor rectal bleeding. Unexplained weight loss may also be a sign of the disorder.

In young children, the most common symptoms are steatorrhoea, weight loss, abdominal distension, and slow growth/failure to thrive, but irritability, vomiting and tiredness are common. It has been suggested that some cases of autism may be caused by coeliac disease.

In adults, the symptoms of coeliac disease may be mistaken for irritable bowel syndrome (IBS) or an inflammatory bowel syndrome such as Crohn's disease. However, coeliac disease is also associated with anemia, cardiomyopathy, depression, fatigue and "mental fog," dental problems (see below), female infertility (particularly miscarriage), peripheral neuropathy, and according to some studies, schizophrenia. A very high proportion of patients diagnosed with dermatitis herpetiformis are coeliacs.

Selective dietary deficiencies such as dietary iron deficiency, vitamin B12 deficiency, osteoporosis (due to Vitamin D and calcium malabsorption), or other secondary dietary deficiencies may be the sole symptom (predominantly in older patients), or found in addition to diarrhea or weight loss. Some coeliacs experience dental problems as a result of malabsorption of nutrients essential for dental health. Coeliacs who have dental symptoms typically have tooth enamel problems, which manifest primarily as discoloration and/or severe tooth decay. A pattern of symmetrical decay is particularly associated with coeliac disease.

Epidemiologically, the disease predominates in Northern European populations. Estimates of its frequency among people of European origin range from 1 in 300 to 1 in 500. Some studies indicate that among the Irish, the frequency may be as high as 1 in 133. Because it is partly genetic, doctors commonly recommend that the first-degree relatives of diagnosed coeliacs should be tested for the disorder even if they are symptom-free.

There is an increased risk of intestinal T-cell lymphoma and osteoporosis in untreated cases. In recent years it has also become more evident that coeliac disease in the pregnant mother could have an adverse effect on the foetus. Offspring to mothers with coeliac disease are more often preterm and low birth weight (weigh less than 2500 grams/5 pounds at birth) than offspring to mothers without coeliac disease. This may be due to the mother's inability to absorb all the nutrients she eats.

A number of patients with other diseases are often screened for coeliac disease, including patients with type 1 diabetes, Down's syndrome, Turner's syndrome, irritable bowel syndrome, lupus, and autoimmune thyroid disease.

Diagnosis

Tests

The gold standard is still upper endoscopy with biopsy of the distal duodenum or jejunum. To avoid false negative results, the first endoscopy must be done while the patient is on a normal, gluten-containing diet or very shortly after going on a gluten-free diet. Sometimes the endoscopy is repeated after the patient has been on a gluten-free diet, in order to ensure that the bowel has healed. However, upper endoscopy always carries a risk of false negative results. This is because coeliac disease may or may not damage villi throughout the entire small intestine, and upper endoscopy only examines the upper part of the intestine. In a patient whose intestinal damage is located further down, the biopsy may come back negative. If the endoscopy is positive the diagnosis is confirmed, but if it is negative, the diagnosis is not necessarily excluded.

Serology has been proposed as a screening measure, because the presence in the blood of IgA antibodies reactive against gluten and tissue transglutaminase is indicative of coeliac disease. Like the endoscopy, these tests are not accurate in patients who have been on a gluten-free diet for some time; they must be performed while the person is on a normal diet or within a relatively short time after eliminating gluten. A thorough workup includes four tests:

Anti-tissue Transglutaminase Antibody (tTG), IgA. This test is sometimes used alone. If this test is positive it is highly likely that the patient has celiac disease.
Anti-Gliadin Antibodies (AGA), IgG and IgA. These tests are often useful when testing young symptomatic children, but they are found in fewer coeliacs than Anti-tTG, and their presence does not automatically indicate coeliac disease because they are found in some other disorders. Some people have an IgA deficiency that causes a false negative test; due to this and other factors, the IgA test has a relatively high rate of false negatives.
Anti-Endomysial Antibodies (EMA), IgA. This test is being replaced by the Anti-tTG test because both tests measure the autoantibodies that cause the tissue damage associated with coeliac disease. Many physicians still order this test.
Anti-Reticulin Antibodies (ARA), IgA. Anti-ARA is not ordered as frequently as it once was, because it is less sensitive and less specific than the other tests. It is found in about 60% of people with coeliac disease and 25% of those with dermatitis herpetiformis.

Many doctors will not consider positive blood tests as definitive proof of coeliac disease, but will still require biopsy confirmation. A growing minority consider coeliac disease to be diagnosed where the patient has positive blood tests and shows improved symptoms after the adoption of a gluten-free diet. Because upper endoscopies are uncomfortable, expensive, and may produce false negative results, this group of doctors considers serology tests and a positive response to eliminating gluten from the diet to be sufficient for diagnosis. A small minority of doctors advocate gluten-free diets even for symptom-free patients who have not had an endoscopy but have had a positive blood test, because some confirmed coeliacs are completely symptom-free throughout their lives; in symptom-free patients, the purpose of the diet is to avoid nutritional deficiencies, osteoporosis, and intestinal lymphoma.

Other tests that may assist in the diagnosis are a full blood count, electrolytes, renal function and liver enzymes. Coagulation testing may be useful to identify deficiency of vitamin K, which predisposes patients to hemorrhage.

Biopsy appearance

The standard changes seen under dissecting microscope are loss of villous height and hypertrophy of the crypts. There is often some degree of inflammation with inflammatory cells (plasma cells and lymphocytes) seen in the lamina propria.

Causes

The cause is presently presumed to be:

Partly a genetic susceptibility to the illness (identical twins do not have 100% concordance however).
Together with an environmental agent, probably a virus or other infection, but stress and pregnancy have also been invoked as possible triggers.
It is associated with other autoimmune diseases; these diseases are also probably a combination of susceptibility and infection.

Autoantigens are probably of major importance in the pathogenesis of coeliac disease (transglutaminase), a trait it shares with many other autoimmune diseases; thyroiditis: thyroglobulin, thyroid peroxidase; multiple sclerosis: myelic basic protein, etc.). To some extent infectious agents may increase the risk of certain autoimmune diseases (e.g. Coxsackie B in type 1 diabetes). However, in the case of coeliac disease, there are few proofs of infections triggering coeliac disease. Some researchers have suggested that smoking is protective against coeliac disease. Results on this topic are however inconsistent, and smoking cannot be recommended as a means to avoid developing coeliac disease.

Pathophysiology

Antibodies to the enzyme tissue transglutaminase (tTG) are found in an overwhelming majority of cases, and cross-react to gluten². This has led to the theory that they cause the autoimmune attack on the bowel lining (which is high in tTG), prompted by the continuous stimulation by gluten. This reaction happens almost exclusively in patients with human leukocyte antigen types DQ2 and DQ8, which is inherited in families. The exact cause for this predisposition is still uncertain, but up to 95% of patients carry these genes (although they are also common in the general population in Western countries).

The inflammatory process leads to disruption of the structure and function of the small bowel's mucosa, and causes malabsorption (it impairs the body's ability to absorb nutrients and fat-soluble vitamins A, D, E and K from food).

The targets of the immunologic response are gliadin, hordein, and secalin, proteins contained in the gluten component of wheat, barley, and rye respectively. Traditionally, oats have been included in the list as well, but some recent studies have brought into question whether this is necessary. Maize (corn), sorghum, and rice are considered safe for a patient to consume. They contain types of gluten that do not trigger the disease.

Treatment

In the vast majority of patients, a strict gluten-free diet will relieve the symptoms. A tiny minority of patients suffer from refractory sprue, which means they do not improve on a gluten-free diet. This may be because the disease has been present for so long that the intestines are no longer able to heal. In other patients, the intestinal damage of coeliac disease may have been aggravated by other problems, such as intolerance to the dietary proteins found in eggs, milk, or soy. Just as a person who is allergic to cats may also happen to be allergic to pollen, a patient with coeliac disease may also happen to have other food intolerances that cause similar symptoms.

Epidemiology

It is estimated that 1 in every 133 to 500 persons (up to 3 million) in the United States and Europe are affected by coeliac disease. The disease is not limited to those of European origin; it is found in other races, but the prevalence is not known. Coeliac disease is more common in women than in men. In symptomatic adults, the average delay between onset of symptoms and diagnosis is estimated at 11 years. This lengthy delay appears to be caused by the variety of symptoms associated with the disease, the fact that some coeliacs have no digestive-tract symptoms at all, and lack of widespread, up-to-date information among doctors.

Social impact

Lifelong diet

The lifelong diet can be difficult and socially troublesome, especially in young patients, but it is crucial in order to avoid serious health consequences. The widespread use of wheat byproducts in prepared food, soups and sauces can make dining out very problematic, although certain types of restaurant (e.g., Japanese, Thai, Indian) already offer a wide range of gluten-free menu options. Teenagers in particular occasionally rebel against the dietary strictures and suffer relapses or complications as a result. It is important for celiacs to understand that one does not "get over" celiac disease; it is present for life. It may be helpful for celiacs who feel overwhelmed by the restrictions on their diet to compare their situation with a much more common disease, diabetes: as difficult as it is for celiacs to maintain a gluten-free diet, it is also difficult for diabetics to maintain their diet and they have the additional burden and expense of daily injections of insulin and very frequent blood tests. Also, as celiac disease has become better understood, the availability of gluten-free replacements for everyday treats such as muffins, bagels, pasta and the like has continually improved. This positive trend shows no sign of slowing, so it will become easier and easier to manage a gluten-free diet.

Catholic Church

The Catholic Church teaches that Communion hosts must contain some unleavened wheat, as it believes that the bread served at the Last Supper did. Sufferers of celiac disease who are Catholic cannot safely consume wheat gluten, and this causes conflict if the attendee's church refuses to make an exception². However, gluten-free communion wafers are now widely available. Several bishops and parishoners have also petitioned for a change in church teaching.

Footnotes

Note 1: Dieterich W, Ehnis T, Bauer M, Donner P, Volta U, Riecken EO, Schuppan D. Identification of tissue transglutaminase as the autoantigen of celiac disease. Nat Med 1997;3:797-801. PMID 9212111.
Note 2: For a recent example detailing the complexities of Coeliac disease and the Catholic Church, see this Associated Press article (http://www.msnbc.msn.com/id/5762478/).