Are you born a coeliac, or do you become one?

Coeliac disease is genetic, or hereditary, which means it runs in families, but not everyone who carries the genes develops the disease. 

There are many factors that determine whether or not a person develops coeliac disease during their lifetime. If you have a first-degree relative – a parent, child or full sibling – with coeliac disease, you have a 1 in 10 risk of developing it too.

There are many different symptoms associated with coeliac disease, including bloating, diarrhoea or constipation, chronic fatigue, anxiety, and depression. Some coeliac patients do not even show significant external symptoms, making it important to screen individuals with coeliac disease in their family.

Coeliac disease is a multifactorial disorder, meaning genetic and environmental factors play a role in developing it. A person can be at higher risk for developing the disease because of their genetic makeup, but this does not mean they will develop the disease. 

The key genes involved in coeliac disease risk are the presence in a person of Human Leukocyte Antigen (HLA) genes. There are other non-HLA factors whose role in coeliac disease development are less understood, including gliadin from gluten and other environmental factors. 

Coeliac disease runs in families, but not everyone at genetic risk will develop the disease. In other words, parents can pass on genes to their children, but genetic predisposition is only one of the factors causes a person to develop coeliac disease.

HLA genes help the immune system distinguish between proteins that belong in our body from those made by foreign invaders, such as viruses and bacteria. Around 99% of people with coeliac disease have one of the following HLA gene variants: HLA DQ2.5, HLA DQ8 or HLA DQ2.2, which sometimes trigger the reaction against gluten.

Presence of one of these genes does not mean you will develop coeliac disease. In fact, around 30% of the population carry these risk genes, but only 1% of them will develop coeliac disease.

First-degree relatives of someone diagnosed with coeliac disease should always be screened, even if they are not they are experiencing any symptoms. A first-degree relative of a confirmed coeliac patient has a 1 in 10 risk of developing coeliac disease. 

Second-degree relatives and families with multiple individuals with coeliac disease also have an increased risk of developing the disease. 

The earlier coeliac disease is diagnosed, the easier it will be to avoid serious health problems arising as a result of the condition.

A simple blood test is all it takes to test someone for coeliac disease. People with coeliac disease who are eating gluten will have higher-than-normal levels of certain antibodies in their blood. For the test to be accurate, you must be eating gluten regularly so that your body is producing the antibodies associated with celiac disease.  

If the result is positive, a biopsy sample of tissue from the small intestine will usually be taken to confirm the diagnosis. 

If the result of the blood test and/or biopsy is negative, genetic testing may still be helpful for understanding whether or not a person is genetically predisposed to developing coeliac disease. This is important information to know because you can develop coeliac disease at any age. 

Gluten intolerance, also known as non-coeliac gluten sensitivity, causes coeliac-like symptoms after gluten consumption– bloating, diarrhoea, abdominal pain, chronic fatigue, and others – but does not stem from an autoimmune reaction or cause the same damage to the intestine.

Because the exact cause of gluten intolerance, or non-coeliac gluten sensitivity, remains unknown, experts still do not understand the extent to which it has a genetic component. 

Testing for the HLA gene variants associated with coeliac disease can be done with a blood test or cells scraped from the mouth. Such a test can be useful when a blood screen for coeliac antibodies drew an inconclusive result. A negative test for the HLA variants would rule out coeliac disease.

However, because a positive result for the HLA variants only indicates that a person has a genetic predisposition to coeliac disease, doctors do not recommend screening large swaths of the population. The only useful result is to be negative for HLA, meaning you cannot develop the condition. 

Given that coeliac disease can develop at any age, and that the symptoms can be hard to detect even when real damage is taking place in the small intestine, repeat screening is recommended if you are at higher risk. 

If one of your relatives has been diagnosed with coeliac disease, you should get a blood test that can also include genetic screening. If the genetic test is negative, you can rule out coeliac disease. However, if the blood test for coeliac disease is negative, but you do have one of the genetic variants associated with the condition, it is important to have repeat screens every few years in case you develop the disease later on.