MPO and autoimmune disease: The study cohort consisted of six cases of IgG4-RD, eight cases of autoimmune diseases [five cases of Sjogren’s syndrome, two cases of primary biliary cholangitis (PBC), and one case of SLE], nine cases of AAV (two cases of PR3-ANCA positive AAV and seven cases of MPO-ANCA positive AAV), and 21 cases of unknown disease group.