Complexity and diversity of gastroesophageal reflux disease phenotypes

Gastroesophageal reflux disease (GERD) is defined as a condition which develops when the reflux of gastric contents causes troublesome symptoms, impairs quality of life, or leads to mucosal damage or complications. There are two main phenotypic presentations of GERD, the erosive (ERD) and non-erosive reflux disease (NERD), with the latter one representing up to 70% of GERD spectrum. Moreover, patients with GERD can be clinically subdivided into two distinct syndromes: patients with esophageal and extraesophageal symptoms. The diagnosis of NERD should be supported by the evidence that symptoms are due to reflux episodes on the basis of an excess of acid into the esophagus or a positive correlation between symptoms and acid and/or weakly acidic reflux episodes as evidenced by 24-hour impedance-pH monitoring. Patients with normal esophageal acid exposure and no correlation between heartburn and any kind of chemical reflux are considered affected by functional heartburn and do not pertain to the realm of NERD. They do not usually respond to PPI therapy as further empirical criterion and are included in the large group of functional digestive disorders with the expression of altered generation or perception of symptoms at the esophageal level and can often overlap with functional dyspepsia and irritable bowel syndrome.