Around 10% of close relatives of people with coeliac disease (parents, siblings, children) are at risk of developing the condition. This increases to approximately 70% in twins from the same egg. Genetically- identical twins (unless there is a mutation during development) have nearly identical DNA but differing environmental factors throughout their lives affecting which genes are switched on and off. In those with a predisposition to coeliac disease, following exposure to gluten, both have a high risk of developing coeliac disease. In comparison, twins from separate eggs (non-identical twins) have a very small chance of having the same genetic profile and therefore a much lower risk of developing coeliac disease (11-20%).These percentages support the evidence for a genetic link to coeliac disease.
How common is coeliac disease?
Coeliac disease affects 1 in 100 people, however, only 24% of those with the condition are diagnosed. Almost, half a million people have the condition but have yet to be diagnosed.
The national clinical guideline for IBS recommends that doctors should rule out coeliac disease before diagnosing IBS (which up to 60% of coeliacs are thought to be misdiagnosed with initially). Coeliac disease can affect people of both sexes and all age groups, though for many the condition manifests in later life.