| Characterized by loss of esophageal peristalsis and insufficient lower esophageal sphincter relaxation in response to deglutition. A rare disease with no gender predilection, the peak incidence occurs between 30 and 60 years of age. Although the precise etiology is unknown, it is often thought to be either autoimmune, viral immune, or neurodegenerative. Some familial cases have been reported, but the rarity of familial occurrence does not support the hypothesis that genetic inheritance is a significant etiologic factor. |