AAAS and Achalasia: The selective involvement of the esophageal myenteric plexus in TAS, in contrast to the normal histopathologic findings in the pylorus, implies that the pathophysiology of achalasia in TAS is distinct from primary idiopathic achalasia, potentially reflecting a disease-specific neurodevelopmental or degenerative process linked to mutations in the AAAS gene encoding the ALADIN protein.19