Genetics of irritable bowel syndrome

Abstract

Irritable bowel syndrome (IBS) is one of the most common diagnoses made by gastroenterologists and primary care providers alike, and yet the underlying mechanism remains poorly understood. Family and twin studies suggest that IBS may have a genetic basis. Several candidate gene association studies have been performed, but thus far, they have failed to clearly identify an "IBS gene." Epidemiological studies are needed to facilitate phenotype definition and identify relevant environment risk factors that will need to factor in gene and environment interactions in all future genetic studies. As genetic research in IBS is relatively nascent, much opportunity, as well as many challenges, exists in identifying the genes responsible for IBS.

Figure 1

IBS may be a complex genetic disease caused by multiple genes (represented by genes A–F) with one or multiple genetic variations (arrows) of modest effect responsible for IBS symptoms. The clinical heterogeneity of IBS may perhaps be explained by the underlying genetic heterogeneity.

Figure 2

The serotonin transporter gene (SLC6A4) contains the 5-HTT LPR polymorphism that results in a 44 bp insertion or deletion of repeat elements 6–8 in the promoter region. This polymorphism results in a long and a short transcript with functional differences.