SCN5A and irritable bowel syndrome: Factors that play a key role in the pathophysiology of IBS include genetic predispositions (variation of chromosome 9, mutations in sucrose-isomaltase gene and SCN5A mutation affecting smooth muscle function), present in 2% IBS patients, and physiological ones, such as abnormal motor activity, visceral hypersensitivity and disorders of the immune function of the intestinal mucosa as a result of microinflammation caused by dysbiosis, i.e., a disturbance of the composition and proportions gut microbiota, which is an essential component of gut-brain interactions.