Genetics of inflammatory bowel disease: A reappraisal

The advent of advanced molecular biological techniques in the last two deca des has allowed the study of genetic factors in inflammatory bowel disease (IBD). A variety of techniques have been employed to elucidate the effects of genes, starting with the clinical observations that IBD is more common i n the relatives of patients than the general population, and the consistenc y of clinical features within families. The situation is likely to be much more complicated than single gene disorders, and it is estimated that betwe en 10 and 20 genes may be involved. Genome scanning techniques using micros atellite markers have been employed to highlight areas of chromosomes linke d to disease such as those on chromosomes 12 and 16. In addition associatio n studies of specific genes such as HLA and cytokine genes have been carrie d out on functional or positional grounds. It is likely that a combination of these techniques will be required to elucidate the role of individual ge nes. Recently much work has been focused on genes that may determine clinic al phenotype such as disease extent or severity or the response to treatmen t. Identification of these genes may lead to better targeting of therapy an d prognostication, and they are likely to be easier to identify than diseas e susceptibility genes.