A 38-year-old man is complaining of periodical problematic swallowing of both solid and liquid foods that is observed for many months. Sometimes he develops an intense retrosternal pain, especially after hot beverages. Asphyxia attacks are observed at night. He has no weight loss. His general condition is satisfactory, the skin is of normal color. Examination detects no changes in the gastrointestinal tract. Chest X-ray shows dilation of the esophagus with air-fluid levels in it. Make the right diagnosis: