Idiopathic achalasia

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. [Source: Wikipedia ]

OrphaNet reference
Idiopathic achalasia 
May Cause
Achalasia