C3 and immunoglobulin G4-related sclerosing disease: Previous studies demonstrated that sex, serum levels of C3, C4, and CH50, new-onset diabetes mellitus, and extensive multi-organ involvement were factors influencing the clinical course of patients with IgG4-RD without treatment.[8,10,12] Additionally, high serum levels of IgG and IgG4, and Mikulicz disease also cause poor clinical course of IgG4-ROD during steroid treatment.[5,6,13] We did not examine serum levels of C3, C4, and CH50 in our case.