[Clinical Practice and Examination for IgG4-Related Disease]

IgG4-related disease (IgG4-RD) is a systemic chronic disease characterized by tumefactive lesions, elevated levels of serum IgG4, and prominent infiltration of IgG4-positive plasma cells with fibrosis. Both lacrimal and salivary glands and the pancreas are the most affected organs during the clinical course of IgG4-RD. The existence of common characteristics associated with IgG4 and frequent overlapping of both diseases has contributed to the establishment of IgG4-RD as a systemic entity. Patients with IgG4-RD are often asymptomatic in the early stage and constitutional symptoms are rarely observed. A typical facial appearance, thirst, and submandibular swelling are initial symptoms that aid in the diagnosis. On suspecting IgG4-RD based on the swelling of various organs, the measurement of serum levels of IgG4 and histopathological examinations including immunostaining with anti-IgG4 antibody are performed, and diagnosis should be made according to comprehensive diagnostic criteria. In addition, careful examination is necessary to exclude other disorders, such as malignancy. Although organ damage in IgG4-RD is thought to be reversible with a favorable responsiveness to glucocorticoids (GC), a delay in treatment intervention causing irreversible dysfunction has been reported. Accordingly, the significance of early diagnosis and therapy has been recognized. Although the first-line treatment for IgG4-RD is empirically the administration of GC, careful observation without treatment may be possible on considering the age and complications. However, severe organ damage such as obstructive jaundice and hydronephrosis is a clear indication for prompt intervention. Multiple organ involvement and subjective symptoms also necessitate treatment.