Mapping susceptibility loci for inflammatory bowel disease

Chronic inflammatory bowel diseases are relatively frequent diseases with an annual incidence of 8/100,000 inhabitants in the North of France(1). There have been variations in both the time and geographic location of this incidence which suggest a role of environmental factors which may be associated with the Western life style. In addition, a genetic predisposition to inflammatory bowel diseases (IBD) has been long suspected, given the existence of ethnic and familial aggregations of these diseases. This susceptibility appears to be, at least in part, common to both types of diseases. Thus, Crohn's disease (CD) and ulcerative colitis (UC) are both more frequent in white populations and both diseases are frequently found in the same families. The relative risk of IBD for a first degree relative of an affected individual is ten times and fourteen times higher than the general population for CD and UC respectively. Two predisposing genes, presently not identified, have recently been localised. Chronic IBD thus appear as multifactorial diseases in which genetic factors and environmental factors cooperate in their development. Additional epidemiological and genetic studies would enable the dissection of these factors and thus provide a precise mechanism which could serve as the basis for new therapeutic research.