Autoimmune Pancreatitis

It has recently been elucidated that there is a group of patients with duct-narrowing pancreatitis in whom steroid therapy is very effective [17, 18]. Since this group of patients often has other autoimmune diseases such as Sjögren syndrome, and their serum 7-globulin, IgG, or particularly, IgG4, often shows a high value, the autoimmune mechanism has been suggested as the cause of this particular form of chronic pancreatitis, and it was named autoimmune pancreatitis [19-21]. In autoimmune pancreatitis, narrowing of the pancreatic ducts due to dense lymphoplasmacytic infiltration is seen [22, 23] (fig. 3a). These inflammatory cells are distributed especially within and around the pancreatic ducts, and often include a significant number of IgG4-positive plasma cells (fig. 3b). This contrasts with other types of chronic pancreatitis in which only mild infiltrations of inflammatory cells are usually seen, and IgG4-positive plasma cells are, if any, usually not so many. Inter- and intralobular fibrosis admixed with acinar atrophy are characteristics observed in autoimmune pancreatitis (fig. 3c), contrasting with the fibrosis pattern of CAP. Also, inflammatory processes sometimes cause obliterative phlebitis in autoimmune pancreatitis, contrasting with CAP, whereby thrombosis of the splenic vein is the usual finding.

Fig. 3. Autoimmune pancreatitis. a Periductal lymphoplasmacytic infiltration and narrowing of the pancreatic ducts are evident. HE. X20. b Some of the narrowing is caused by IgG4-positive plasma cells. Immunostain for IgG4. X60. c Diffuse inter- and intralobular fibrosis as well as acinar atrophy is marked in this disease. HE. X40.

Fig. 3. Autoimmune pancreatitis. a Periductal lymphoplasmacytic infiltration and narrowing of the pancreatic ducts are evident. HE. X20. b Some of the narrowing is caused by IgG4-positive plasma cells. Immunostain for IgG4. X60. c Diffuse inter- and intralobular fibrosis as well as acinar atrophy is marked in this disease. HE. X40.

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