A 20-year-old woman presents with a 2-year history of difficulty swallowing and increasing fatigue. A CBC shows Iron-deficiency anemia. Upper endoscopy reveals an annular narrowing in the upper third of the esophagus. A mucosal biopsy shows no evidence of inflammation or neoplasia. Which of the following is the most likely diagnosis?
Achalasia Barrett esophagus Diveiculum Esophageal web