Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Achalasia

What Is It?

Achalasia is an uncommon disorder of the smooth muscle of the esophagus, the muscular tube that carries food from the mouth to the stomach. Normally, coordinated contractions of this smooth muscle, known as peristaltic waves, move food through the esophagus.

Between the esophagus and stomach is a special muscle called the esophageal sphincter (LES). This muscle surrounds the esophagus to keep it closed and prevent food and acid from splashing back up into the esophagus from the stomach. When you swallow, this sphincter relaxes and opens to allow food to pass into the stomach. At the same time, nerves coordinate the contractions of the esophagus so that food is moved when the sphincter opens. In achalasia, the nerve cells in the lower two-thirds of the esophagus and the sphincter are abnormal. This causes uncoordinated or weak peristaltic waves and causes the sphincter to remain closed, making it difficult for food to pass from the esophagus into the stomach.

The cause of achalasia is unknown. Studies show that the nerves that control the muscle contractions of the esophagus have deteriorated. Why this happens is unclear. There have been theories that a viral infection leads to nerve damage but these theories have not been proven. Another possibility is that the body's immune system attacks and destroys the nerves.

Approximately 2,000 new cases of achalasia are diagnosed each year in the United States.

Other conditions besides achalasia can cause the esophagus to function improperly, including diffuse esophageal spasm, polymyositis or dermatomyositis, hypothyroidism and scleroderma esophagus.