300 IgG4-RD patients, 200 other autoimmune diseases, 60 IgG4-RD mimickers and 100 healthy controls were enrolled. Circulating plasmablast/plasma cells were detected of all patients at baseline and healthy controls. IgG4-RD patients were followed up every 3-6 months. Circulating plasmablast/plasma cells were also detected at disease remission and relapse. IgG4-RD patients' clinical data and laboratory parameters were collected.

300 IgG4-RD patients, 200 other autoimmune diseases, 60 IgG4-RD mimickers (pancreatic cancer, cholangiocarcinoma, vasculitis, lymphoproliferative diseases, inflammatory bowel disease, kimura disease) and 100 healthy controls were enrolled. Peripheral blood samples of 5-10 ml were collected from all patients and healthy controls. Serum was separated for ELISA detection. Circulating plasmablast/plasma cells were detected of all patients at baseline and healthy controls. IgG4-RD patients were followed up every 3-6 months. Circulating plasmablast/plasma cells were also detected at disease remission and relapse. IgG4-RD patients' clinical data and laboratory parameters were collected. Data were analyzed to evaluate plasmablast/plasma cells in diagnosis and relapse prediction of IgG4-RD.

Inclusion Criteria:

• IgG4-RD patients fulfilled the 2011 comprehensive diagnostic criteria of IgG4-RD (2011). Other autoimmune disease and IgG4-RD mimickers fulfilled the corresponding diagnostic criteria.

Exclusion Criteria:

• Patients in pregnancy or preparing to pregnancy, patients with active infection, including HIV, HCV, HBV, TB, et al.

300 IgG4-RD patients, 200 other autoimmune diseases, 60 IgG4-RD mimickers (pancreatic cancer, cholangiocarcinoma, vasculitis, lymphoproliferative diseases, inflammatory bowel disease, kimura disease) and 100 healthy controls were enrolled.