Idiopathic achalasia is confined to the esophagus and has no established etiology , with agenesis of the myenteric plexus or viral infections , in particular herpes simplex ( HSV - 1 ) , the most likely hypothesis . In Brazil , the secondary achalasia caused by Chagas disease predominantly among other etiologies , involves but is expressed primarily systemic disease with esophageal involvement . Infected patients Typanossoma cruzi, the causative agent of Chagas disease , 7-10 % have esophageal involvement, and due to its chronic nature the most common clinical presentation is megaesophagus , to varying degrees .