Tubular duplication of the esophagous is a rare congenital malformation where a second structure with individual lumen and stratified squamous mucosa and muscularis mucosa lies within or adjacent to the true esophagus causing dysphagia, nausea, vomiting, retrosternal pain and respiratory problems (stridor and recurrent pneumonia) and usually presenting in children. The disease is Monarch Disease Ontology term MONDO_0015051 (tubular duplication of the esophagus).