Achalasia is a neuromuscular failure of relaxation at the lower end of the oesophagus with progressive dilatation, tortuosity, incoordination of peristalsis and often hypertrophy of the oesophagus above. There is effectively a functional obstruction at the lower end of the oesophagus.
Achalasia may occur at any age but particularly in the third to fourth decades. Males and females are affected equally.
Incidence is about 1 per 100,000 per year.