Achalasia is primarily a disorder of motility of the lower oesophageal or cardiac sphincter. The smooth muscle layer of the oesophagus has impaired peristalsis and failure of the sphincter to relax causes a functional stenosis or functional oesophageal stricture. Most cases have no known underlying cause but a small proportion occurs secondary to other conditions - eg, oesophageal cancer.
This is a companion discussion topic for the original article at https://patient.info/doctor/achalasia-pro