IgG4-related disease (IgG4-RD) is a multi-system immune disease. An elevated serum level of IgG4 is one of the characteristics of IgG4-RD and can be used as an index for preliminary screening. While IgG4-RD often mimics a variety of disorders, such as malignant, infectious and other immune diseases, and patients may start their visit based on the most obvious clinical manifestations, many studies have found that elevated serum IgG4 could also be detected in patients with other systemic disorders like lymphoma, systemic lupus erythematosus (SLE), granulomatosis with polyangiitis, so the final diagnosis is heavily dependent on the doctor's familiarity with the disease.