Aetiology

Achalasia involves degeneration of the myenteric plexus and vagus nerve fibres of the lower oesophageal sphincter (1):

• neurological defect involving the ganglion cells of Auerbach's myenteric plexus in the lower oesophageal sphincter and oesophageal body
• abnormalities in the vagal dorsal motor nucleus, the nucleus ambiguous, and in the smooth muscle of the oesophagus.

The damaging agent has been variously hypothesised as a neurotoxic virus, an autoimmune process, and a genetic predisposition (1).

Secondary achalasia can be seen in:

• Chagas' disease caused by Trypanosoma cruzi
• gastric carcinoma that results in oesophageal infiltration
• eosinophilic gastroenteritis
• lymphoma
• neurodegenerative disorders
• viral infection

At its most severe, aperistalsis occurs in the lower two thirds of the oesophagus with normal peristalsis above it:

• food accumulates in the oesophagus which becomes dilated and atonic
• prolonged transit time may be a factor in the increased incidence of malignancy with achalasia - in up to 5% of cases.

Reference:

(1) Momodu II, Wallen JM. Achalasia. [Updated 2021 Aug 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan- Available from: https://www.ncbi.nlm.nih.gov/books/NBK519515/ - article-17083.s4 (accessed 21 January 2022)