Achalasia, a disorder of the digestive system, most commonly manifests between the ages of 20 and 40. While it can occur in different age groups, 5% of cases appear in childhood. The exact cause of achalasia is unknown, but a reduction in ganglion (nerve) cells in the muscle layer at the lower end of the esophagus is implicated. Possible contributing factors include:

Genetic
Infectious
Toxic and autoimmune causes