[ORDER SOLUTION] GI case study

A 60-year-old man presents to the clinic with a 3-month history of gradually worsening dysphagia (difficulty swallowing). He first noticed the problem when eating solid food such as steak, but now it happens even with drinking water. He has a sensation that whatever he swallows becomes stuck in his chest and does not go into the stomach. He has also developed worsening heartburn, especially upon lying down, and has had to prop himself up at night to lessen the heartburn. He has lost 10 kg as a result of his swallowing difficulties. His physical examination is unremarkable. A barium  (Links to an external site.)  swallow x-ray reveals a decrease in peristalsis of the body of the esophagus along with dilatation of the lower esophagus and tight closure of the lower esophageal sphincter. The distal esophagus and lower esophageal sphincter have a beaked appearance. There is very little passage of barium into the stomach. What is the likely diagnosis in this patient, and what is the underlying pathophysiology of this condition? Botulinum toxin can be used to treat this disorder. How does it help ameliorate the symptoms? What are the possible complications of this disorder, and how do they arise?