IgG4-related sclerosing cholangitis and Type I autoimmune pancreatitis

Type 1 autoimmune pancreatitis (AIP) is a prototype of IgG4-related disease (IgG4-RD) and IgG4-related sclerosing cholangitis (IgG4-SC) is the biliary manifestation of IgG4-RD. Recently, IgG4-RD is wellrecognized as a systemic disease affecting most organs and the diagnosis criteria in each organ has been established or is currently being researched. Both extrahepatic bile ducts and pancreatic ducts of the ventral pancreas embryologically originate from the common duct in the 4th fetal week. In addition to the similarities in their histogenesis and histology, similarities in AIP and IgG4-SC are also recognized such as prominent IgG4-positive cells, storiform-type fibrosis, and obliterative phlebitis in their affected portions. Although the diagnosis of IgG4-RD is relatively easy in surgical specimens, the tiny mucosal surface specimens obtained by biopsy procedure do not contain enough material to reach a definitive diagnosis. Moreover, the presence of IgG4-positive cells in tissue and increased serum IgG4 levels are often found in patients with biliary and pancreatic cancers. The diagnosis of IgG4-RD in the pancreatiobiliary system, especially in biopsy specimens, is clinicopathologically necessary to consider every possibility. © 2017 by Nova Science Publishers, Inc. All rights reserved.[Book Chapter