Failure of normal relaxation of the lower esophageal sphincter associated with uncoordinated contractions of the thoracic esophagus, resulting in functional obstruction and difficulty swallowing.

Esophageal achalasia, often referred to simply as achalasia, is a failure of smooth muscle fibers to relax, which can cause the lower esophageal sphincter to remain closed. Without a modifier, "achalasia" usually refers to achalasia of the esophagus...