Achalasia is a primary motor disorder of the esophagus. It is characterized by aperistalsis and a failure of the lower esophageal sphincter to relax due to a loss of inhibitory nitrinergic neurons in the esophageal myenteric plexus. Patients typically present with dysphagia, regurgitation, retrosternal pain, and substantial weight loss (summary by Farrokhi and Vaezi, 2007 and Gockel et al., 2010). [from
OMIM]