Sunday 9 February 2014

How common is coeliac disease?

How common is coeliac disease?

This follows from the previous post Is there really an epidemic of coeliac disease?”

The characteristic syndrome of coeliac disease is rare. It usually will develop in children when, following a milk-only diet, weaning to cereals takes place. The child will fail to gain weight, develop diarrhoea and be generally unwell. After coeliac disease is diagnosed the change to a gluten-free diet will be followed by a rapid improvement.

If coeliac disease is diagnosed in adult life it is assumed that it has been present since early childhood and has been clinically latent. It can be diagnosed at any age, even among the elderly. The presentation would be with anaemia, shortage of iron and folic acid, low weight and diarrhoea.

The new simple blood test allows the testing of people in whom there is no suspicion of coeliac disease, and this allows an estimate of its frequency in the general population. The result is quite remarkable and it now appears that about 90% of people with coeliac disease are undiagnosed. They are walking around happily and taking a normal diet.

But many of them might not be as well as they think. Some will have low-grade abdominal symptoms, often classified as an irritable bowel. If they are demonstrated as having coeliac disease, then a gluten-free diet might give them a sense of health better than they had previously experienced.

Testing for coeliac disease in adults should be considered in circumstances such as irritable bowel syndrome, symptoms being abdominal discomfort after eating, with bloating and diarrhoea.  The testing should be considered especially if there are other pointers such as low weight or weight loss, and iron deficiency anaemia. It can however be diagnosed in people who are overweight.

Irritable bowel symptoms are so common in society that many people accept them as just part of life, and indeed they are often just features of normal intestinal physiology. There comes a time when they interfere with life and this is when a visit to the doctor comes about. Hitherto undiagnosed coeliac disease might then be diagnosed by the simple blood test. 

What harm does it do?

It is vital that this is understood, otherwise justification for “treatment” will make no sense.

In the early 1970, when I was taking Crosby capsule biopsies, case reports came out in the medical journals of various gastro-intestinal cancers in adults who had been diagnosed as coeliac disease in childhood. This was thought to be a big problem, and that very strict adherence to a gluten free diet was imperative to avoid cancer. We thus entered an area of medicine by fear, and this still exists: “You must keep to a very strict gluten free diet or will develop cancer”.

Experience now tells us that these case reports were exceptional and that there is no excess of common gastro-intestinal cancers in coeliac disease. There is however an increase of a very rare form of intestinal lymphoma, but it remains rare. A large community based study of coeliac disease from Nottingham UK, as opposed to previous and biased hospital based reports, indicates a very minimal increase in deaths from intestinal lymphoma, and rather surprisingly a significant reduction of deaths from lung and breast cancers. So coeliac disease is far from being all bad news.

The risk of rare lymphoma has become far less than originally thought. In the past, without up-to-date information, we have been basing risk on only the 10% of coeliac disease patients that have been diagnosed. When we consider all people now assessed as having coeliac disease, the risk of lymphoma immediately reduces by a factor of ten, and this is a big factor.

The purpose of treatment therefore changes from cancer prevention and life prolongation to treatment of the illness, if indeed there is an illness. When coeliac disease has been diagnosed it is worth trying a gluten free diet. If it improves the abdominal symptoms then the person diagnosed will want to continue the diet. Some will find that they are extremely sensitive to gluten and that just a tiny amount will cause symptoms that might persist for several days.

On the other hand some people will notice no benefit. Although they have undoubtedly being diagnosed as having Gluten Enteropathy (disease of intestine caused by gluten), strictly speaking do they really have coeliac disease if they are coming to no harm?