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 illustrate the systemic and organ-specific findings of IgG4-RD. This book shows a systematic and organ-specific evaluation of immunological and radiological findings for general practitioners. Moreover, the book is also interesting for the subspecialists including rheumatologists, dermatologists, otologists, respiratory physicians, clinical immunologists and radiologists, and patients and their families because patients with IgG4-RD visits every subspecialist by the tremendous various clinical symptoms and findings. The study in the book included 147 patients with IgG4-RD who visited Saga University Hospital from 1 January 2001 to 31 March 2020. Although the number of patients studied in this monograph was not so large, the patients evaluated and treated by a single institution are considered clinically valuable.