A 54-year-old man with a long history of indigestion after meals and "heaburn" presents with upper abdominal pain. He was treated with proton-pump inhibitors for gastroesophageal reflux 3 years . An endoscopic biopsy of the lower esophagus shows glandular metaplasia. The patient described is at increased risk of developing which of the following diseases of the esophagus?
Achalasia Adenocarcinoma Candidiasis Plummer-Vinson syndrome