Prevalence of IgG4-related disease in Japan based on nationwide survey in 2009

The number of patients with autoimmune pancreatitis who visited hospitals in Japan in 2007 was approximately 2709 (95 confidence interval; range 25403040). Because IgG4-related disease is a new clinical entity, there are no data with regard to its prevalence. To estimate the number of patients with IgG4-related disease in Japan, we randomly selected hospitals using stratification and asked them how many patients they had with IgG4-related disease in 2009. The number of patients with Mikuliczs disease, IgG4-related retroperitoneal fibrosis, IgG4-related renal disease, IgG4-related pulmonary disease, and IgG4-related lymphadenopathy who visited hospitals in Japan in 2009 was approximately 4304 (95 confidence interval; range 33605048), 272 (95 confidence interval; range 264306), 57 (95 confidence interval; range 4766), 354 (95 confidence interval; range 283424), and 203 (95 confidence interval; range 187240), respectively. The total number of patients with IgG4-related disease without autoimmune pancreatitis in Japan was approximately 5190 (95 confidence interval; range 41416084). The male:female ratio was 1:0.77, and the average of age of disease onset was 58.8 years. The total number of patients with IgG4-related disease in Japan in 2009, including autoimmune pancreatitis, was approximately 8000.