Linking Genotype with Phenotype in Inflammatory Bowel Disease – Will We Ever Have Reagent Standard Patients?

Genetic factors predispose to a number of gastrointestinal diseases. The spectrum of genetic determination may vary from classical inherited diseases such as haemochromatosis where the genetic mutation is now fairly well defined to complex polygenic diseases, such as inflammatory bowel disease and coeliac disease. In inflammatory bowel disease, genetic predisposition confers disease susceptibility, but epigenetic factors (lifestyle or environmental triggers) are required to manifest the disease phenotype. The relatively rapid rise in incidence of inflammatory bowel disease especially Crohn’s disease in some populations, such as children in Scotland [1], suggest that environmental triggers are likely to be very important, as the genotype of a cohort is unlikely to change so rapidly. The Scottish data confirms rapid temporal changes implicating environmental factors in the aetiology of both Crohn’s disease and ulcerative colitis, and the relationship between the temporal changes of Crohn’s disease and ulcerative colitis suggest certain shared risk factors. Preliminary prospective data for paediatric patients in the whole of UK show the same trend [2]. As the in-