That the coeliac condition has a genetic component is demonstrated by the fact that it tends to run in families. Family members of coeliacs are approximately ten times more likely than the general population to suffer from the condition. However, not all of the numerous genes that contribute to a hereditary predisposition are presently known. The best-understood factors belong to the human leukocyte antigen (HLA) system, a complex of genes that “recognise” molecules foreign to the organism. The HLA-DQ2 and/or DQ8 genotypes are present in the vast majority (at least 95 per cent) of coeliacs. The presence of HLA-DQ2/DQ8 alone, however, does not necessarily lead to a development of the illness, as these same genes are found in a high percentage of healthy subjects (20 to 3 0 per cent of the general population).
The environmental component of the coeliac disorder is an exposure to gluten in the diet.