What happens in untreated coeliac disease?

When someone with coeliac disease eats gluten, the immune system reacts by damaging the lining of the gut. In a healthy gut there are tiny, finger-like projections called 'villi' that allow the body to absorb nutrients from the food we eat into the bloodstream.

In untreated coeliac disease, these villi become inflamed and can become flattened and even disappear. Typical flattening of the villi seen in coeliac disease is called 'villous atrophy'.  When the gut lining is damaged in this way, it means the body can't absorb all the nutrients from food properly, a process called 'malabsorption'.

The biopsy picture below shows the villi of a healthy gut:

This is a biopsy from someone with untreated coeliac disease. The villi have disappeared.

The flattening of the gut villi and the malabsorption of nutrients causes many of the symptoms of coeliac disease and contributes to the health risks associated with coeliac disease such as anaemia and osteoporosis.

The abnormal immune response can affect other parts of the body, causing for example the skin rash dermatitis herpetiformis (DH).