Coeliac disease (also called celiac disease, non-tropical sprue, c(o)eliac sprue, gluten enteropathy and gluten intolerance) is a digestive disorder in genetically-predisposed individuals. The only susceptibility locus established is the HLA-DQ. It is characterised by damage or flattening to all or part of the villi lining the small intestine, causing scar tissue that cannot absorb nutrients. This damage is caused by exposure to gluten (gliadin) and related proteins found in wheat, rye, malt, barley and oats.
Signs and symptoms
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, such as indigestion, heartburn and 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.
Other symptoms can include dermatitis (an itchy rash), diarrhea, excessive tiredness or fatigue, aching in joints and a general feeling of being unwell.
Coeliacs (people with coeliac disease) may also be symptom-free, but they are still doing damage to their small intestines. Regardless of the presence or absence of symptoms, the disorder is associated with an increased risk of osteoporosis and MALT lymphoma, a form of intestinal cancer.
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 (or even obesity occasioned by overeating due to cravings for nutrients), indigestion, acid reflux, excessive tiredness (coeliacs have reported falling asleep while driving) and an itchy rash (dermatitis) may also be a sign of the disorder. Delayed puberty (or short stature prior to adolescence) might also be a symptom. Rarely, coeliacs may experience symptoms similar to those of sinus infections and/or the formation of thick, choking plugs or ropes of mucus that require considerable effort to expel. A low-grade, persistent pain may be present, possibly lessened by eating, which may all too easily be taken for the presence of ulcers.
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 disease such as Crohn's disease. However, coeliac disease is also associated with anemia, cardiomyopathy, depression, fatigue and "mental fog," dental problems (see below), adverse pregnancy outcome (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), poor thyroid function, 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.
The condition is frequently misdiagnosed or overlooked as it can exhibit multiple symptoms and often the patient or medical staff may not link seemingly unconnected conditions. It is most frequently misdiagnosed when the sufferer complains of diarrhea, persistent indigestion, a rash or irritable bowel syndrome.
The gold standard test for c[o]eliac disease 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 gliaden 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 few months after eliminating gluten from the diet. 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. tTG test is not reliable in children before the age of 2.
- 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 . They are unable to mount an IgA response to any antigen and will have false negative tests for the IgA type celiac tests.
- 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. This test as tTG test is also not reliable in children before the age of 2.
The cause is presently presumed to be:
- Partly a genetic susceptibility to the illness.
- 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.
- Possible exposure to gluten as a young baby before the gut barrier has developed fully (though this is still subject to further research).
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.
The timing of the first exposure to gluten is also thought to be important. Children who were exposed to gluten between the ages of four and six months were less likely to exhibit coeliac disease later in life.
In July 2005, University of Colorado scientists published information on their studies, which indicated that exposure to gluten in the first three months of a baby's life increased the risk of coeliac disease five-fold. This is believed to be a result of gluten crossing the baby's relatively undeveloped gut barrier. However, after the baby is six months old, the risk appears to be less. There is ongoing research in this area.
Coeliac disease has been identified in some diabetics or people suffering from milk allergies; there is some debate in medical circles as to whether these conditions are linked to gut damage caused by the disease.
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.
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. In rare cases only the complete removal of members of the Gramineae family of plants from the diet will bring about recovery from symptoms.