Esophageal complications of GERD include erosive esophagitis, esophageal ulcer, esophageal stricture, and Barrett’s esophagus (i.e., standard lining of stratified squamous epithelium in the distal esophagus is replaced by a metaplastic simple columnar epithelium with mucin-secreting goblet cells, also called specialized intestinal metaplasia) that may lead to esophageal adenocarcinoma [117]. Here, MUC5AC is linked to Barrett esophagus.