Frequency and clinical characteristics of special types of achalasia in Japan: a large-scale, multicenter database study.

BACKGROUND AND AIM Achalasia is a rare disease, with an incidence of one in 100 000. Genetic factors and autoimmune involvement have been reported in its etiology, and their involvement is strongly suspected, especially in patients with familial achalasia and those with comorbid hereditary or autoimmune diseases. However, these special types of achalasia are rare, and their frequency and clinical characteristics remain unclear. METHODS This retrospective, multicenter cohort study included Japanese patients with a diagnosis of achalasia, treated between 2010 and 2019 across six tertiary centers in Japan. The frequency and clinical characteristics of special types of achalasia, namely, familial achalasia, achalasia with a comorbid hereditary disease, and achalasia with a comorbid autoimmune disease, were retrospectively investigated using a large-scale multicenter database. RESULTS During the study period, 1115 patients were treated for achalasia at six tertiary centers. Familial achalasia, achalasia with a comorbid hereditary disease, and achalasia with a comorbid autoimmune disease occurred in 7 (0.63%), 11 (0.99%), and 27 (2.4%) patients, respectively. Familial achalasia had a slightly younger age of onset (37.6 ± 12.1 years old) and a higher incidence in male patients (six patients; 85.7%). Down's syndrome was the most common hereditary comorbidity, and thyroid disease was the most common autoimmune comorbidity. CONCLUSIONS We clarified the frequency and clinical characteristics of special types of achalasia. Although special types of achalasia are rare, these comorbidities should be considered when treating patients with achalasia.