الفهرس 
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Abstract
Gastroesophageal reflux disease (GERD) is a multifactorial process, one of the most common diseases which is significant for its prevalence, variety of clinical presentations, under recognized morbidity, together with significant economic consequences.
GERD is a spectrum of disease usually producing symptoms of heartburn and acid regurgitation. Most patients have no visible mucosal injury at the time of endoscopic examination (nonerosive GERD), whereas some have esophagitis, peptic strictures, Barrett’s esophagus, or evidence of extra esophageal diseases such as chest pain, pulmonary symptoms, or ear, nose, and throat symptoms.
Barrett’s esophagus is the condition in which a metaplastic columnar mucosa (of intestinal type), replaces an esophageal squamous mucosa damaged by gastroesophageal reflux disease.
In patients with long standing GERD which leads to chronic esophageal injury, Barrett’s metaplasia develops when mucus-secreting columnar cells replace reflux-damaged esophageal squamous cells. The cells that give rise to this metaplasia are not known. It has been proposed that GERD might induce alterations in the expression of key developmental transcription factors, causing mature esophageal squamous cells to change into columnar cells (trans differentiation) or causing immature esophageal progenitor cells to undergo columnar rather than squamous differentiation (trans commitment).