IgG4-related disease (IgG4-RD) is an increasingly recognized and novel systemic inflammatory disorder characterized by tumefactive lesions with infiltrating IgG4-positive plasma cells. The disease affects virtually every organ system. Immunologically, plasmablasts increase in patients with IgG4-RD in which activation and dysregulation of B cells may be involved. Accurate characterization by a method using various modalities and immunological evaluation including plain radiography, ultrasound, CT, scintigraphy, MRI and flow cytometry should be required. Comprehensively, we review and...