Our study found that compared with IgG4-RD-non-RPF, the levels of eosinophils, IgG4 and IgG4/IgG were significantly decreased, and the levels of neutrophils, C3 and C4 were increased in IRPF patients, which indicated that the pathogenesis of the two diseases was different. Here, C3 is linked to immunoglobulin G4-related sclerosing disease.