Achalasia is a disorder of the esophagus characterized by the inability of the lower esophageal sphincter (LES) to relax properly. This leads to difficulty swallowing (dysphagia), regurgitation of undigested food, and chest pain. The condition results from the degeneration of nerve cells in the esophagus, affecting the normal movement and function of the esophagus, making it difficult for food to enter the stomach.
