A statistically significant increase in the expression of the pro-inflammatory cytokine TNF-α was found in the mucosal biopsy of IBS patients from duodenum compared to healthy individuals (3.5 ± 0.5 versus 1.1 ± 0.3 points, respectively), ileum (3.6 ± 0.5 and 1.1 ± 0.3, respectively), cecum (5.4 ± 0.5 and 1.0 ± 0.2) and sigmoid colon (5.6 ± 0.5 and 1.2 ± 0.3; p < 0.0001 for all localizations; Fig 1). This evidence concerns the gene TNF and irritable bowel syndrome.