Overlap FGIDs and Genetic Polymorphism

Inclusion Criteria: FGID group * No organic diseases in routine laboratory tests, abdominal imaging, esophagogastroscopy, and colonoscopy * NERD or reflux hypersensitivity (RH): typical heartburn occurring at least once a week without visible esophageal mucosal break detected by endoscopy * FD or IBS: based on the Rome III criteria Control group \- Subjects who underwent GI evaluations as part of health check-up or for other problems, such as mild abdominal discomfort or pain for a relatively short period of time, but had no organic problems during GI endoscopy Exclusion Criteria: * history of GI surgery except appendectomy * inflammatory bowel disease * any malignancy, or systemic diseases requiring chronic medication except for hypertension and diabetes mellitus * pregnant or lactating women * hepatic, biliary, or psychiatric disorders requiring medication.