The Future of Molecular Approaches to Inflammatory Bowel Disease Boyko Kabakchiev, Smita Halder and Mark S. Silverberg Mount Sinai Hospital Inflammatory Bowel Disease Group, Dr Zane Cohen Digestive Diseases Clinical Research Centre, University of Toronto, Toronto, Ontario, Canada Contents Abstract .......................................................................................................... 217 1. Etiology and Pathogenesis of Inflammatory Bowel Disease (IBD) ........................................................ 217 2. Clinical Diagnosis of IBD and Limitations of Existing Approach .......................................................... 218 2.1 Preclinical .................................................................................................. 218 2.2 Diagnosis .................................................................................................. 218 2.3 Prognosis ................................................................................................... 218 3. Limitations with the Existing Approach .............................................................................. 219 4. Genomics ...................................................................................................... 219 5. Transcriptomics ................................................................................................. 220 6. Proteomics ..................................................................................................... 220 7. Systems Biology and IBD .......................................................................................... 221 Abstract Technological advances in genomics and transcriptomics have resulted in the introduction of molecular tests into the clinical arena. Despite established uses of such tests in the oncology field, their integration into the management of complex diseases has not been widely evaluated. Progress in the field of inflammatory bowel disease (IBD) genetics has been rapid in recent years, and these advances have provided more urgent impetus to investigating the role of molecular tests in IBD. This article summarizes the current state of molecular testing available for IBD, and the potential utility of such tests as research in the area widens. Inflammatory bowel disease (IBD) comprises a group of conditions affecting the gastrointestinal (GI) tract, character- ized by chronic and relapsing immune activation and inflam- mation. There are two main forms of IBD, ulcerative colitis (UC) and Crohn’s disease (CD), although a heterogeneous spec- trum of clinical presentations can occur. In about 10% of cases patients do not conform to established diagnostic criteria and are then classified as having indeterminate colitis or IBD un- classified. [1] The incidence rate of IBD is in the range of 2–8 per 100 000 people per year, and the prevalence rate can be as high as 319 per 100 000. [2,3] IBD tends to be a disease of young adulthood, with CD generally having an earlier age of onset than UC. There is no known sex preponderance in adult-onset IBD, although males predominate in very-early-onset IBD. [4] IBD is more common in developed countries, and migration studies have demonstrated that people who immigrate into developed areas increase their risk with each generation. [5] 1. Etiology and Pathogenesis of Inflammatory Bowel Disease (IBD) IBD is a complex disorder thought to result from an in- appropriate activation of the mucosal immune system by enteric bacteria in genetically susceptible hosts. It is heterogeneous in respect of age of onset, location, extent, and behavior of REVIEW ARTICLE Mol Diagn Ther 2009; 13 (4): 217-223 1177-1062/09/0004-0217/$49.95/0 ª 2009 Adis Data Information BV. All rights reserved.