What is Coeliac Disease?
Coeliac disease is a permanent, lifelong inflammatory disease of the upper small intestine and result from gluten ingestion in genetically susceptible individuals. This causes damage to the lining of the intestines. This leads to poor absorption of important nutrients including iron, folic acid, calcium, and fat-soluble vitamins. Gluten is a protein found mainly in wheat and to a lesser extent in rye, oats and barley. Hence the alternative name for the condition is Gluten-sensitive Enteropathy. Coeliac Disease is closely related to dermatitis herpetiformis. In dermatitis herpetiformis, skin rash and a similar small intestinal enteropathy to that of coeliac disease are typically present, and both respond to withdrawal of gluten.
Is Coeliac an Autoimmune disease?
Coeliac disease is associated with a variety of autoimmune disorders. Increased incidence of Rheumatoid Arthritis, diabetes mellitus, autoimmune thyroid disease, sarcoidosis, vasculitis and pulmonary fibrosis has been reported in coeliac patients. The prevalence of coeliac disease among children with diabetes (IDDM) is 50 times more likely than chance. IgA deficiency is 10 times more common in coeliac patients than in the general population. Patients with coeliac disease and selective IgA deficiency often have circulating antibodies to food proteins; they also have circulating immune complexes, suggesting that absence of an intestinal barrier might allow the absorption of antigenic material from the gut. Antibodies to some antigens might cross react with the host's self-components and might indirectly produce autoimmune disease.
How common is Coeliac?
Studies show coeliac to be a more common disorder than previously thought, possibly affecting up to 1 in 300 of the general population. The majority of patients finally diagnosed in adulthood usually in the 30-45 year age group. As a result, many other cases may not be discovered and are often falsely diagnosed as Irritable bowel Syndrome (IBS). In fact only about one third of cases are ever diagnosed as coeliac disease and appropriately treated with a gluten-free diet. Untreated coeliac disease is associated with long-term risks such as osteoporosis and gastrointestinal malignancy.
Does it run in families?
Yes, it certainly can. The incidence in first-degree relatives (parents, siblings) is about 10-15% if a family member (parent or sibling) has Coeliac Disease.
What is the difference between Coeliac Disease & wheat Allergy?
Although the precise cause of coeliac is unknown, T cells may play a central role. A T cell-mediated or Type 4 (Delayed Hypersensitivity Immune response) to gluten is likely to be the major cause of the gut lesions and increased permeability to gluten and other foods. T cells may react with tissue glutaminase (the principal component of the endomysium auto antigen) and set in motion a series of inflammatory events that results in the classical coeliac mucosal lesion. Wheat Allergy, on the other hand, is a Type 1 (Immediate Hypersensitivity Immune response) where wheat protein causing excessive production of IgE antibodies. These IgE antibodies sit on mast cells & when the intestine comes in contact with wheat, they bind to the IgE antibodies & cause the mast cell to release histamine & other mediators. These excessive IgE antibodies to wheat can be measured in the blood by doing a RAST or a Skin Prick Test. This is usually seen in an atopic individual & commonly associated with eczema. In wheat allergy the individual will only react to wheat, whereas in coeliac they react to all gluten-containing cereals such as wheat, oats, barley & rye.
What are the symptoms?
Most gastroenterologists recognise that Samuel Gee's description of coeliac disease in 1888 is now an uncommon presentation – but most general practitioners' image of coeliac disease is still of this classic form. Recent advances, driven by Antibody blood tests have lead to the realisation that clinically overt cases represent only a small proportion of patients with the disorder. The classical symptoms are malabsorption of food and chronic diarrhoea associated with anaemia, failure to grow, abdominal distension, offensive bulky stool and mouth ulcers. This is usually seen in infants less than 2 years of age, usually when they are weaned off milk onto solids. This fulminant presentation is now uncommon, and as paediatric patients tend to present at a later age (median 4 years), features such as loss of appetite and a short stature may predominate.
Intestinal symptoms may be absent in adults with coeliac disease. In adults, the disease often presents in a milder form, and therefore easily missed – especially with non-specific symptoms such as fatigue, vague abdominal pains, intermittent diarrhoea and slight anaemia. The most likely presentation is a combination of microcytic anaemia, past or present, a family history of the disease, and feeling tired all the time.
How is coeliac disease diagnosed?
Small intestine biopsy
The "gold standard" for diagnosing coeliac disease is still a biopsy of the small intestine. This can be done with or without sedation. A specimen is taken from the distal end of the duodenum via an upper gastrointestinal endoscopy. The specimen is scrutinized microscopically for flattening of the normal villi (folds) in the lining of the intestine as in this diagram.
The coeliac screening blood test measures antibodies in the blood to gluten or gliaden in the diet (ant gliadin antibody) and the damaged Endomysial muscle of the bowel (Endomysial antibodies).
With the advent of the Endomysial antibody test, blood (serological) diagnosis of coeliac disease has come to the forefront. Endomysial antibodies are closely associated with gluten sensitive disease, and in appropriate clinical setting coeliac disease can be diagnosed with 100% specificity. As the assay depends on the detection of IgA antibodies, the endomysial antibody test is obviously negative in individuals with IgA deficiency (which is 10 times more common in coeliac disease), but is also negative in a proportion of other patients; however a sensitivity of 86% or greater has been observed. Assays for antigliadin antibody can help in this situation, enabling almost all patients to be identified.
Screening for Coeliac Disease
It is useful to screen first-degree relatives of known coeliacs, those presenting with vague symptoms, or other at-risk patients.
Both Antigliadin antibody & anti-endomysial antibody tests are usually done along with IgA levels. The anti-endomysial test is more reliable, and is useful in screening of undiagnosed Coeliacs. People who have already commenced a gluten free diet will not be suitable for this test. Advantages of the blood screening are that it is non-invasive, and relatively inexpensive. Disadvantages are that it is not diagnostic. A positive test at this stage still requires a small bowel biopsy.
How is Coeliac Disease Managed?
- Initiate a strict gluten free diet. (Not Low gluten). When considering gluten content, it is useful to consider foods in 3 groups:
Those that contain gluten
Wheat, wheatmeal, wheat germ, rye, oats, oatmeal, oat bran, barley, triticale, pasta, semolina, farina, bread, biscuits, batter, crumbs, malt, malt flavouring, malt extract.
Those that may contain gluten (depending on source)
Modified starch, thickening agents (1400 -1450), maltodextrin, dextrin, dextrose, hydrolysed protein, glucose, glucose syrup, caramel (colour), foods containing component ingredient (eg baking powder).
Those that are definitely gluten free
Rice, rice bran, rice flour, corn, maize flour, maize meal, polenta, potato flour, buckwheat, arrowroot, chickpea flour, pea flour, Soya flour, lentils, lentil flour, sago, tapioca, amaranth.
- Ensure regular consultation with a trained dietician
- Add supplements of deficient nutrients – for example, iron, folic acid, calcium
- Monitoring – Annual blood tests to determine improved health status, including:
- Antigliadin levels (normal range can be achieved on a gluten free diet)
- Iron studies
- Folate & B12
- Bone Density Test – should be performed initially & about every 5 years
- Repeat intestinal biopsy if clinical progress is suboptimal.