IgG4-related disease.

Immunoglobulin G4-related disease (IgG4-RD) is a regional or systemic fibro-inflammatory disease of unknown etiology. It presents a distinctive histopathological appearance of dense lymphoplasmacytic infiltrates with abundant IgG4-positive plasma cells, storiform fibrosis and obliterative phlebitis with the appearance of inflammatory swelling or tumefactive lesions. This new disease entity includes a wide variety of diseases such as Mikulicz disease, autoimmune pancreatitis, Riedel thyroiditis, interstitial nephritis and retroperitoneal fibrosis. Glucocorticoid therapy can resolve the clinical and pathological abnormalities and impaired organ function. IgG4-RD was recognized internationally in 2011, and new evidence has accumulated regarding its pathogenesis, clinical features and treatment. In this review, we outline our present understanding of IgG4-RD.