- IgG4-RD is an immune-mediated fibroinflammatory condition that is capable of affecting multiple organs.
- It is characterized by multi-organ involvement, serum IgG4 elevation, and infiltration of the affected organs with IgG4-positive plasma cells
- Type 1 Autoimmune pancreatitis is one of the most common features of this systemic syndrome.
- IgG4-related sclerosing cholangitis (IgG4-SC) is cholangitis associated with elevated serum IgG4 levels, dense infiltration of IgG4-positive plasma cells with storiform fibrosis, and/or obliterative phlebitis in the bile duct wall and good response to glucocorticoids
- IgG4-SC and type 1 AIP often overlap as a pancreatobiliary syndrome within the IgG4-RD spectrum.
- Organs typically involved in IgG4-RD include the pancreas (type 1 AIP); bile duct (sclerosing cholangitis); submandibular, parotid, and sublingual glands (sclerosing sialadenitis); orbital area with lacrimal gland involvement (sclerosing dacryoadenitis often associated with Mikulicz disease); lung; retroperitoneum (fibrosis); and kidney (tubulo-interstitial nephritis).