Q. A 56-year-old male presents to your clinic with a chief complaint of heartburn and regurgitation for the past 6 months. He reports having a burning sensation in his chest after meals that sometimes wakes him up at night. He also reports losing weight, as he has difficulty eating due to the symptoms. He has tried over-the-counter antacids, but they provide limited relief. His medical history is significant for hypertension and type 2 diabetes. He is a former smoker and drinks alcohol occasionally. He is taking lisinopril and metformin for his hypertension and diabetes, respectively. On physical examination, he is found to have tenderness in the epigastric region and a positive Santorini's sign. You refer him for a barium study (see image). The barium study reveals a circumferential narrowing of the lower esophagus and grade C esophagitis. Which of the following is the most likely underlying etiology of his symptoms?