Background:Immunoglobulin G4-related disease (IgG4-RD) is a newly recognized systemic disease that can involve multiple organs and various clinical phenotypes.The purpose of this study was to analyze different types of organ involvement in IgG4-RD patients in China.Methods:We conducted a prospective cohort study on IgG4-RD patients to analyze the clinical manifestations and rare features of IgG4-RD.Patients were grouped into different types according to organ involvement regarding organ number and organ site.The constituent ratio in different types was also analyzed.Results:A total of 200 IgG4-RD patients,with a male:female ratio of 2.08:1,were grouped into different types.Cases having involvement of two or three organs were the most common whereas the fewest number of patients had multi-organ (≥4) involvement.Serum IgG4 and IgE levels,IgG4/IgG ratio,and percentage of eosinophils increased as the number of involved organs increased.In addition,constituent ratio analysis revealed that patients with salivary gland/lacrimal gland swelling,who also constituted the largest number of IgG4-RD patients,had higher serum IgG4 concentrations and IgG4/IgG values,had higher percentage of Eos,and were more likely to have had a history of allergies relative to patients with intal organ involvement.Conclusions:The characteristic feature of IgG4-RD is multiple organ involvement with various clinical manifestations and different types.Although serum IgG4 levels increased with the number of involved organs,serum IgG4 levels were higher for those patients with salivary gland/lacrimal gland swelling compared with those with intemal organ involvement.Thus,valuable clues to the differential diagnosis of IgG4-RD could be obtained by examining the clinical patts of organ involvement.