The etiology of achalasia remains uncertain. Proposed mechanisms for the disease include genetics, infectious agents, autoimmune destruction, and primary neural degeneration. Various case reports have identified instances of both horizontal and vertical 'transmission'.19-24 The majority of these familial cases, however, occur in the setting of consanguinity. While this raises the possibility of a rare, recessive gene being expressed, a large-scale study of more than 1000 first-degree relatives of patients with achalasia showed no affected relatives - contrary to expected Mendelian genetics.25
Five per cent of patients with chronic Chagas' disease develop poor LES relaxation and mega-esophagus that mimics classic achalasia,26 which suggests that an infectious etiology of achalasia is possible. The protozoan Trypanosoma cruzi which causes Chagas' disease acts through direct invasion of cells, toxin production or antigenic factors to cause degeneration of esophageal neurons. The mechanism of this process is also uncertain, and may be from direct injury to neurons of the esophagus, an inflammatory reaction or the generation of autoantibodies against these nerves.27 Potential infectious candidates for idiopathic achalasia include measles and varicella viruses, but as yet no firm evidence exists to confirm this associa-tion.25'28-31
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