Coeliac disease in Middle Eastern countries: a challenge for the evolutionary history of this complex disorder?

Abstract

About 10,000 years ago domestication and farming of wheat and other cereals developed in the 'Fertile Crescent', an area including modern Turkey, Iraq and Iran. Agriculture then slowly spread from Middle East to Europe. Coeliac disease is the permanent intolerance to dietary gluten, the major protein component of wheat. It has been until relatively recently hypothesised that wheat consumption exerted a negative selective pressure on genes predisposing to coeliac disease, eventually leading to higher coeliac disease frequency in Northeastern Europe because of lack of exposure to cereals. This theory is at variance with recent studies showing that coeliac disease is as common in Middle Eastern countries as in Europe. High prevalence of coeliac disease has been found in Iran, in both the general population and at-risk groups, e.g. patients with irritable bowel syndrome or type 1 diabetes. Clinical manifestations of coeliac disease vary markedly with the age of the patient, the duration and the extent of disease. Clinical studies showed that presentation with non-specific symptoms or no symptoms is as common in the Middle East as in Europe. Wheat represented a major component of the Iranian diet for many centuries and it may be argued that the continuous and high level of exposure to wheat proteins has induced some degree of immune tolerance, leading to milder symptoms that may be misdiagnosed as irritable bowel syndrome or unexplained gastrointestinal disorders. The gluten-free diet represents a real challenge to both patients and clinicians in this area. This is particularly difficult in the absence of any supply for gluten-free diet in Middle Eastern countries.