Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder. It is characterized by symptoms of abdominal pain, bloating, and abnormal bowel movements, such as diarrhea or constipation. In IBS, there appears to be no organic substance or biochemical abnormality that can explain the symptoms. IBS can be classified into categories: constipation predominant IBS (IBS-C), diarrhea predominant IBS (IBS-D), mixed IBS (IBS-M), and un-subtyped IBS. Anticholinergic drugs, 5-HT3 receptor antagonist, high molecular weight polymers (polycarbophil calcium), gastrointestinal motility regulators, probiotics preparations, and laxatives are used in the treatment of IBS. However, they are not uniformly effective. Several studies of patients with IBS suggest that this disorder aggregates in families, and thus, appears potentially heritable. It has been reported that familial GUCY2C diarrhoea syndrome shares clinical characteristics with IBS-D.
