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Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Oct 28, 2015; 21(40): 11353-11361
Published online Oct 28, 2015. doi: 10.3748/wjg.v21.i40.11353
Genetic epidemiology of irritable bowel syndrome
Jasbir Makker, Sridhar Chilimuri, Jonathan N Bella
Jasbir Makker, Sridhar Chilimuri, Jonathan N Bella, Department of Medicine, Bronx-Lebanon Hospital Center and Albert Einstein College of Medicine, Bronx, NY 10457, United States
Author contributions: Makker J wrote the manuscript; Chilimuri S and Bella JN is the senior author who critically reviewed and revised the manuscript.
Conflict-of-interest statement: Authors have no conflict of interest to disclose.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Jonathan N Bella, MD, Department of Medicine, Bronx-Lebanon Hospital Center and Albert Einstein College of Medicine, 12th Floor, 1650 Grand Concourse, Bronx, NY 10457, United States. jonnbella@earthlink.net
Telephone: +1-718-5185222 Fax: +1-718-5185585
Received: April 20, 2015
Peer-review started: April 21, 2015
First decision: May 18, 2015
Revised: June 16, 2015
Accepted: August 25, 2015
Article in press: August 25, 2015
Published online: October 28, 2015
Abstract

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder characterized by presence of abdominal pain or discomfort associated with altered bowel habits. It has three main subtypes - constipation predominant IBS (C-IBS), diarrhea predominant IBS (D-IBS) and IBS with mixed features of both diarrhea as well as constipation (M-IBS). Its pathophysiology and underlying mechanisms remain elusive. It is traditionally believed that IBS is a result of multiple factors including hypersensitivity of the bowel, altered bowel motility, inflammation and stress. Initial studies have shown familial aggregation of IBS suggesting shared genetic or environmental factors. Twin studies of IBS from different parts of world have shown higher concordance rates among monozygotic twins than dizygotic twins, and thus suggesting a genetic component to this disorder. Multiple studies have tried to link single-nucleotide polymorphisms (SNPs) to IBS but there is little evidence that these SNPs are functional. Various molecules have been studied and investigated by the researchers. Serotonin, a known neurotransmitter and a local hormone in the enteric nervous system, has been most extensively explored. At this time, the underlying gene pathways, genes and functional variants linked with IBS remain unknown and the promise of genetically-determined risk prediction and personalize medicine remain unfulfilled. However, molecular biological technologies continue to evolve rapidly and genetic investigations offer much promise in the intervention, treatment and prevention of IBS.

Keywords: Irritable bowel syndrome, Single-nucleotide polymorphism, Serotonin, Familial aggregation, Genetics

Core tip: Irritable bowel syndrome (IBS) is believed to result from interplay of several factors including hypersensitivity of the bowel, altered bowel motility, inflammation and stress. Familial aggregation of cases and twin studies underscore the genetic basis of IBS. Different researchers have studied several candidate genes but the evidence so far linking IBS to specific genes is inconsistent and weak. Genome wide association studies that can examine several common genetic variants are needed to design newer drugs and diagnostic methods.