Achalasia - A disease of the esophagus caused by the abnormal function of nerves and muscles of the esophagus that makes swallowing difficult. There may sometimes be chest pain. Regurgitation of undigested food can occur, as can coughing or breathing problems due to entry of food into the lungs. The underlying problems are weakness of the lower portion of the esophagus and failure of the lower esophageal sphincter to open and allow passage of food. Achalasia may occur at any age but is predominantly a disease of young adults. Diagnosis is made by an X-ray, endoscopy, or esophageal manometry (to measure the pressure in the esophagus). Treatment includes medication, dilation (stretching) to widen the lower part of the esophagus, and surgery to open the lower esophagus. A fairly recent approach involves injecting medicines into the lower esophagus to relax the sphincter. .