Achalasia is a rare disorder that affects the esophagus, the tube that carries food from the mouth to the stomach. In this condition, the muscles of the esophagus fail to relax properly, making it difficult for food to pass into the stomach. This can lead to symptoms such as difficulty swallowing, chest pain, and regurgitation of food. The exact cause of achalasia is not fully understood, but it may involve damage to the nerves in the esophagus. Diagnosis typically involves tests like esophageal manometry and endoscopy. Treatment options include medications, dilation of the esophagus, or surgery to improve swallowing.