Causes of Coeliac disease
Coeliac disease is caused by an abnormal immune reaction in the body which is similar to autoimmune diseases. In the case of coeliac disease, the immune system reacts to otherwise harmless proteins (i.e. gluten in the diet), as if they were harmful, causing an inflammatory reaction in the lining of the small bowel. This inflammation shortens the millions of finger-like villi that line the small bowel and aid in the absorption of nutrients, resulting in villous atrophy. Consequently, the small bowel can develop issues absorbing food, resulting in nutritional malabsorption, and the inflammation can lead to additional gastrointestinal and/or non-intestinal symptoms.
The precise reason why one person develops coeliac disease and someone else does not has yet to be fully understood. However, there are various factors that are associated with a higher probability of developing it.
There is a strong genetic component to coeliac disease. Those with a close family member with coeliac disease, such as a sibling or parent, have about a 10% chance of having it too. Less than one percent of people with coeliac disease do not have at least one of two human leukocyte antigen genetic variants (HLA-DQ2 and/or HLA-DQ8).These genetic variants relate to the human leukocyte antigen complex, a group of proteins that are found on the surface of immune cells that are involved in instructing how the immune system recognises foreign proteins. These genetic variants are common, with about half of the population having either one. The majority of these people will not develop coeliac disease, but because the absence of these genetic variations is rare in people with the condition (i.e. < 1%), a negative test can be used to effectively rule out the possibility of coeliac disease, thus shifting the investigation to other more probable diagnoses.
Environmental and other factors
Several environmental factors have been associated with a greater probability of developing coeliac disease. How they might trigger coeliac disease remains unknown. People that have reported previous infections, especially gastrointestinal ones (e.g. rotavirus), have a higher likelihood of coeliac disease. There is an association between coeliac disease development and higher levels of gluten intake during infancy. A diagnosis of autoimmune diseases such as thyroid disease or type 1 diabetes, or Down syndrome is also associated with a higher risk of coeliac disease.
Untreated coeliac disease and complications
Untreated coeliac disease is associated with various long-term complications, these include-
- Low bone density (i.e. osteopenia) or weakening of the bones (i.e. osteoporosis).
- Lactose intolerance
- Liver disease such as autoimmune hepatitis
- Iron deficiency anaemia (i.e. iron deficiency, causing fatigue/shortness of breath)
- Fertility issues, such as infertility and a higher risk of miscarriage
- Neurological issues (e.g. peripheral neuropathy, movement issues)
- Increased risk of developing some cancers (e.g. Non-Hodgkins lymphoma)
These complications are associated with the chronic inflammation and/or gastrointestinal malabsorption that occurs in untreated coeliac disease. Fortunately, strict removal of dietary gluten can reduce one’s immediate symptoms, and also reduce the risk of long-term complications. The complications discussed here are not an indication of what will happen, but rather describe potential issues that may emerge in people with coeliac disease, especially if it remains undiagnosed or poorly treated.