Within the wall of the oesophagus (gullet) there are nerve fibres which control the muscular contractions which are necessary for normal swallowing to occur.
In some patients these nerve fibres degenerate and the normal contractions within the oesophagus are lost. Furthermore, the sphincter at the junction between the oesophagus and the stomach fails to relax when required.
With time this loss of nerve fibres results in the oesophagus turning into a drain pipe of a tube with a tight junction at its lower end.
The annual incidence is about 1 in 100,000 people with an equal sex incidence. It tends to present in adult life between about 25 and 40 years old with less than 5% occurring in children.