Abstract
Crohn's disease (CD) and ulcerative colitis (UC), also known as inflammatory bowel diseases (IBD), are characterized by chronic inflammation of the gastrointestinal tract. IBD is among the few complex diseases for which several genomic regions and specific genes have been identified and confirmed in multiple replication studies. We will review the different loci implicated in disease risk in the context of three proposed mechanisms leading to chronic inflammation of the gut mucosa: 1) deregulation of the innate immune response to enteric microflora or pathogens; 2) increased permeability across the epithelial barrier; and 3) defective regulation of the adaptive immune system. As our knowledge of genetic variation, analytical approaches and technology improves, additional genetic risk factors are expected to be identified. With the identification of novel risk variants, additional pathophysiological mechanisms are likely to emerge. The resulting discoveries will further our molecular understanding of IBD, potentially leading to improved disease classification and rational drug design. Moreover, these approaches and tools can be applied in the context of variable drug response with the goal of providing more personalized clinical management of patients with IBD.
Acknowledgements
We thank Celine Lefebvre and Claudia Reinhard for their helpful comments on the manuscript. The authors have no conflicts of interest to report. RJX is supported by National Institute of Allergy and Infectious Diseases and Center for Inflammatory Bowel Disease, Massachusetts General Hospital. JDR is supported by grants from the National Institute of Allergy and Infectious Diseases, the NIDDK and the Crohn's and Colitis Foundation of America.