Although understanding to the detailed mechanism of these cells in IgG4-RD is still limited, the pathological features of IgG4-RD suggest potential roles of these cells in the fibrosis of IgG4-RD: in recent studies, mild to moderate eosinophil infiltration was observed in the affected tissues, and increased peripheral blood eosinophil count and serum IgE level were detected in IgG4-RD patients (2, 26, 27), which suggests that Eos may tightly related to the pathogenesis of IgG4-RD. The gene discussed is IGHE; the disease is immunoglobulin G4-related sclerosing disease.