Mapping susceptibility loci in inflammatory bowel disease: why and how?

The cause of the inflammatory bowel diseases Crohn's disease and ulcerative colitis is unknown, but epidemiological evidence suggests that it is multifactorial with a strong genetic component. Several genetic loci probably contribute to disease susceptibility, accounting for the complex pattern of inheritance and heterogeneous clinical manifestations. The combination of candidate gene studies and, more recently, genome-wide searches has resulted in the identification of a number of putative susceptibility loci. With large-scale, fine-mapping studies under way, and accelerating progress in the physical mapping of the human genome, rapid progress is now being made towards the identification of the genes responsible for inflammatory bowel disease.