Recent Advances in the Concept and Pathogenesis of IgG4-Related Disease in the Hepato-Bilio-Pancreatic System

Recent studies have proposed nomenclatures of type 1 autoimmune pancreatitis (AIP) (IgG4-related pancreatitis), IgG4-related sclerosing cholangitis (IgG4-SC), IgG4-related cholecystitis, and IgG4-related hepatopathy as IgG4-related disease (IgG4-RD) in the hepato-bilio-pancreatic system. In IgG4-related hepatopathy, a novel concept of IgG4-related autoimmune hepatitis (AIH) with the same histopathological features as AIH has been proposed. Among organs involved in IgG4-RD, associations with pancreatic and biliary lesions are most frequently observed, supporting the novel concept of "biliary diseases with pancreatic counterparts." Targets of type 1 AIP and IgG4-SC may be periductal glands around the bile and pancreatic ducts. Based on genetic backgrounds, innate and acquired immunity, Th2-dominant immune status, regulatory T (Treg) or B cells, and complement activation via a classical pathway may be involved in the development of IgG4-RD. Although the role of IgG4 remains unclear in IgG4-RD, IgG4-production is upregulated by interleukin 10 from Treg cells and by B cell activating factor from monocytes/basophils with stimulation of toll-like receptors/nucleotide-binding oligomerization domain-like receptors. Based on these findings, we have proposed a hypothesis for the development of IgG4-RD in the hepato-bilio-pancreatic system. Further studies are necessary to clarify the pathogenic mechanism of IgG4-RD.

Recent Advances in the Diagnosis and Management of Autoimmune Pancreatitis: Similarities and Differences in Japan and Korea

Two subtypes (types 1 and 2) of autoimmune pancreatitis (AIP) are currently recognized. Type 1 AIP is related to immunoglobulin G4 (lymphoplasmacytic sclerosing pancreatitis), and type 2 AIP is characterized by neutrophilic infiltration into the epithelium of the pancreatic duct (idiopathic duct-centric pancreatitis). Although type 2 AIP is sometimes observed in the United States and Europe, most cases of AIP in Japan and Korea are type 1. The international consensus diagnostic criteria for AIP were created to be applicable worldwide and to distinguish between the two types of AIP. AIP is diagnosed based on the presence of at least one of the five cardinal features (i.e., imaging, serology, other organ involvement, histology, and response to steroid therapy). Oral steroids are the standard therapy for AIP, but immunomodulatory drugs or rituximab have been successfully used for patients with relapsed AIP in the United States and Europe. Generally, the clinical manifestations and demography of AIP are similar between Japan and Korea. However, there are differences in some aspects of the disease, including the proportion of other organ involvement, the prevalence of type 2 AIP, diagnostic criteria and maintenance therapy between the two countries.

Conference Report: Korea-Japan Symposium on Autoimmune Pancreatitis

A consensus meeting on autoimmune pancreatitis (AIP) was held in Seoul on August 31, 2007. Many Korean and Japanese gastroenterologist interested in AIP participated in the joint symposium, and issues related to histology, radiology, clinical manifestation, serology, and diagnostic criteria were discussed. This joint meeting indicated the need for unified diagnostic criterion for AIP in Korea and Japan. Here, we provide a summary of the symposium presentations and discussions.