<unk> , often referred to simply as<unk> , is a failure of smooth muscle fibers to relax, which can cause the lower esophageal sphincter to remain closed. Without a modifier,<unk> " usually refers to<unk>  of the esophagus.<unk>  can happen at various points along the gastrointestinal tract;<unk>  of the rectum, for instance, may occur in Hirschsprung's disease. The lower esophageal sphincter is a muscle between the esophagus and stomach that opens when food comes in. It closes to avoid stomach acids from coming back up. A fully understood cause to the disease is unknown, as are factors that increase the risk of its appearance. Suggestions of a genetically transmittable form of<unk>  exist, but this is neither fully understood, nor agreed upon.<unk>  is an esophageal motility disorder involving the smooth muscle layer of the esophagus and the lower esophageal sphincter (LES). It is characterized by incomplete LES relaxation, increased LES tone, and lack of peristalsis of the esophagus (inability of smooth muscle to move food down the esophagus) in the absence of other explanations like cancer or fibrosis.<unk>  is characterized by difficulty in swallowing, regurgitation, and sometimes chest pain. Diagnosis is reached with esophageal manometry and barium swallow radiographic studies. Various treatments are available, although none cures the condition. Certain medications or Botox may be used in some cases, but more permanent relief is brought by esophageal dilatation and surgical cleaving of the muscle (Heller myotomy). The most common form is primary<unk> , which has no known underlying cause. It is due to the failure of distal esophageal inhibitory neurons. However, a small proportion occurs secondary to other conditions, such as esophageal cancer, Chagas disease (an infectious disease common in South America) or Triple-A syndrome.<unk>  affects about one person in 100,000 per year. There is no gender predominance for the occurrence of disease. The term is from a- +<unk>  "no relaxation."<unk>  can also manifest alongside other diseases as a rare syndrome such as<unk>  microcephaly.
Esophageal achalasia
Esophageal spasm
Nutcracker esophagus
Esophagogastric junction outflow obstruction
Esophageal web
Megaesophagus
Diffuse esophageal spasm
Esophageal stricture