A novel clinicopathological entity of “IgG4-related sclerosing disease” has been proposed, based on histological and immunohistochemical examination of various organs of patients with autoimmune pancreatitis (AIP). This is a systemic disease that is characterized by extensive IgG4-positive plasma cell and T lymphocyte infiltration of various organs. Clinical manifestations are apparent in organs where tissue fibrosis with obliterative phlebitis is pathologically induced. AIP may be a pancreatic lesion reflecting an IgG4-related sclerosing disease. This disease includes AIP, IgG4-related sclerosing cholangitis, IgG4-related cholecystitis, IgG4-related sialadenitis, IgG4-related retroperitoneal fibrosis, IgG4-related tubulointerstitial nephritis, IgG4-related interstitial pneumonia, IgG4-related prostatitis, and IgG4-related inflammatory pseudotumor. Many cases are associated with IgG4-related lymphadenopathy. Most IgG4-related sclerosing diseases have been found to be associated with AIP, but IgG4-related sclerosing diseases without pancreatic involvement have been reported. In some cases, only 1 or 2 organs are clinically involved, while in others 3 or 4 organs are affected. The disease occurs predominantly in elderly males and responds well to steroid therapy. Serum IgG4 levels and immunostaining with anti-IgG4 antibody are useful in making the diagnosis. Since malignant tumors are frequently suspected on initial presentation, IgG4-related sclerosing disease should be considered in the differential diagnosis to avoid unnecessary surgery.
Keywords: IgG4-related sclerosing disease, autoimmune pancreatitis, IgG4, sclerosing cholangitis, retroperitoneal fibrosis, IgG4 Associated Sialoadenitis, Chronic Pancreatitis, Idiopathic Pancreatitis, Salivary Gland Diseases, Chronic Sialoadenitis, extrapancreatic lesions