Update on inflammatory bowel disease genetics.

The idiopathic inflammatory bowel diseases (IBD), comprised of Crohn's disease (CD) and ulcerative colitis (UC), are related, complex genetic disorders. With the completion of the human genomic sequence, identification of genetic variants contributing to IBD susceptibility can now more systematically be identified. Significant genetic linkages have been observed on chromosomes 16, 12, 14, 19, 6, and 1, of which the linkage to CD on chromosome 16 is the most well-established. For many of the other regions, evidence for linkage has been observed for both CD and UC. Candidate gene association studies have largely focused on genes involved in inflammatory pathways, such as cytokines and cytokine receptors. With greater understanding of genetic differences underlying both disease susceptibility and response to medical therapy, the individualization of medical approaches based on this knowledge may soon be possible in patients with IBD.