Epidemiological features of immunoglobulin G4-related sclerosing cholangitis in Japan.

BACKGROUND/PURPOSE: Epidemiological data on immunoglobulin G4-related sclerosing cholangitis (IgG4-SC) are scarce. METHOD: We randomly selected healthcare facilities from a list of all facilities in Japan. The selection rate was determined according to a stratification based on the facility characteristics and scale. We sent questionnaires to the selected facilities enquiring about the number and sex of patients with IgG4-SC in 2018. Among responding facilities, we further inquired about the clinical characteristics of the patients with IgG4-SC. RESULTS: We selected 1180 departments from health centers across Japan. Of them, 532 (45.1%) responded to the questionnaires. The number of reported patients with IgG4-SC was 1045, and the estimated point prevalence was 2.18 (95% confidence interval, 2.13-2.23) per 100 000 population. In addition, we enrolled 1096 patients with IgG4-SC, combining data from previously and newly registered patients. Male patients comprised 79.5% of the population and patients aged 60-80 years had the highest risk for developing the disease. The follow-up period was 5.1 ± 4.0 years and the 5- and 10-year overall survival rates were 95.3% and 89.0%, respectively. CONCLUSIONS: The point prevalence of IgG4-SC was 2.18 per 100 000 population. The epidemiological features were similar to those observed in previous studies.