Coeliac Disease

Coeliac Disease is an auto-immune condition caused by an immune reaction to a small part of a protein called gluten, which is found in wheat. The offending protein fragment is only 33 amino acids long and only provokes an abnormal immune response in those with a genetic predisposition following ingestion of gluten and exposure to envirometal triggers.

 

The genetic factors associated with Coeliac disease are genes associated with the special proteins which are displayed on the surface of certain cells involved in the co-ordination of immune responses (HLAs, - thos with susceptibility to coeliac disease carry HLA DQ2 or DQ8. There are numerous proteins within this system which do not confer a risk of coeliac disease. HLA DQ2 or DQ8 are carried by approximately 10-20% of the population, but only a fraction of people with such proteins ever get the disease.

 

A second necessary pre-requisite for development of the disease is exposure to gluten, which is contained in wheat containing products. However most people with HLA DQ2 or DQ8 do not usually go on to get coeliac disease unless they ar also exposed to an environmental trigger. At present a number of candidates appear to be potential triggers including rota-viruses and enteroviruses, which infected the gut and presumably increase the leakiness of the gut lining leading to a greater exposure of the antigenic fragment (the small part of gluten that provokes the initial immune response), and then a triggering of an irreversible change in the immune system that then renders the individual a sufferer of coeliac disease. This change in the immune system then leads to inflammation within the lining of the bowel in affected individuals.

 

In classical coeliac disease the once numerous and slender finger-like processes (villi) that optimise the available absorptive surface of the gut become shrunken (atrophied) and crypts (small pits in between the villi) deepen. Of course not all patients have such florid changes and so doctors grade the changes according to a classification known as the Marsh classification. This grades changes from zero, normal, to four,  complete flattening of the vilii with considerable infiltration of the  lining of the gut by inflammatory cells called lymphocytes.

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Patients with coeliac disease may present with gut symptoms, abdominal pain, bloating, diarrhoea or constipation, failure to thrive, weight loss or anaemia, often associated with deficiency of other vitamins. Many patients are entirely asymptomatic and are diagnosed whilst undergoing investigation for other conditions, such as reccurent miscarriage or numbness and tingling in the limbs.

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Treatment is almost exclusively by exclusion of gluten from the diet, which leads to healing of the mucosa and settling of the immune response – provided no further gluten is ingested. In patients who do not respond to gluten exclusion this is usually because gluten is slipping into the diet accidentally or without the patient knowing (resistant coeliac disease- Type 1). Rarely some patients have  a persistent immune response despite a strictly gluten free diet. These patients are at risk of small bowel T-cell lymphoma and require specific drug therapy (Resistant coeliac disease- type 2)