- Failure of the lower esophageal sphincter (LES) to relax.
- Primary achalasia: associated with loss of ganglion cells in the esophageal myenteric plexus.
- Secondary achalasia is relatively uncommon. Etiologies include certain malignancies, diabetes mellitus, and Chagas disease.
 Imaging Findings
- The distal esophagus is narrowed and has been described as resembling a bird's beak.
Patient #1: Classic appearance of achalasia on radiographs
Patient #2: Achalasia in a patient with Allgrove syndrome