Current concept, diagnosis and pathogenesis of autoimmune pancreatitis as IgG4-related disease.

Recently, autoimmune pancreatitis, a pancreatic manifestation of IgG4-related disease (IgG4-RD) has been recognized as a novel clinical entity associated with massive infiltration of IgG4-positive cells. The first international symposium on IgG4-RD endorsed the comprehensive nomenclature as IgG4-RD, which the Japanese research committee supported by the Ministry of Health, Labor and Welfare of Japan proposed in 2009, and proposed the individual nomenclatures for each organ system manifestations and the international pathologic consensus in 2011. In addition to the pathological consensus, the Japanese comprehensive diagnostic criteria (CDC) for IgG4-RD for general use, and several organ specific criteria for the organ specified physicians have been proposed; the International Consensus Diagnostic Criteria and the revised clinical diagnostic criteria in 2011 by Japan Pancreas Society (JPS-2011) for type1 AIP, the Clinical Diagnostic Criteria 2012 for IgG4-sclerosing cholangitis (IgG4-SC-2012), the diagnostic criteria for IgG4-positive Mikulicz's disease by the Japanse Society for Sjogren's syndrome, and Diagnostic criteria for IgG4-related kidney disease by the Japanese Society of Nephrology. Although the pathogenic mechanism still remains unclear, we have proposed a hypothesis of the pathogenic mechanism; abnormal innate and acquired immunity, regulatory T cells, and B cells on abnormal genetic backgrounds may be involved in the development of IgG4-cholangiopathy. Further studies are necessary to clarify the pathogenesis including genetic backgrounds, disease specific antigens, and the role of IgG4.