(a, b) CT findings in a 67-year-old female with pancreatic head swelling. (a) CT at diagnosis in May 2005 showing pancreatic head swelling (arrows). (b) CT 27 months later in August 2007 showing pancreatic stone formation (arrows) and pancreatic atrophy. (c, d) ERP and CT findings in a 69-year-old male with narrowing of both the Wirsung and Santorini ducts. (c) ERP at diagnosis in April 2001 showing Wirsung and Santorini duct narrowing (arrowheads). (d) CT 105 months later in December 2009 showing pancreatic stone formation (arrows) and pancreatic atrophy (Data are reprinted from Ref.  with permission from the Journal of Gastroenterology)
Clinical features, laboratory tests, and pancreatic morphology at diagnosis
Stone-forminggroup (n = 28)
Non–stone-forminggroup (n = 32)
Pancreatic morphology at diagnosis
Pancreatic swelling (by CT)
Ductal narrowing in MPD (by ERP)
Wirsung + Santorini (+/−)
Pancreatic Stone Formation and Pancreatic Function
It is essential to confirm whether pancreatic stone formation in AIP is associated with pancreatic exocrine or endocrine dysfunction, as is the case in ordinary chronic pancreatitis. To clarify this, we compared serum values of amylase and HbA1c (JDS) at diagnosis, 5 years, and 8 years among non–stone-forming patients, stone-forming patients, and intraductal stone-forming patients, who seemed to be at a more advanced stage of stone formation. Although we found no significant differences among the groups, both serum amylase and HbA1c values tended to be at abnormal levels in intraductal stone-forming patients compared with non–stone-forming patients (Table 25.2) . We consider that further study may reveal a significant deterioration of pancreatic exocrine or endocrine function in stone-forming patients, although stone-forming AIP might have a different pathophysiology from that of ordinary chronic pancreatitis.
Serum values of amylase and HbA1c during the study course
Intraductal stone-formingpatients (n = 9)
5 years later
8 years later
5 years later
8 years later
Epidemiology of Pancreatic Calcification
Other reports presenting the frequency of pancreatic calcification in AIP have cited ranges from 4 to 40 % [3, 6–10, 12, 18–20]. Hart et al. conducted an international investigation of 659 patients with AIP and reported that 46 patients (7 %) showed pancreatic calcification, which had a significant correlation with relapse . The frequency of the pancreatic calcification in these results was generally lower than that of our findings, which might be because of differences in disease activity, observation period, therapeutic method, and especially maintenance therapy.
Autoimmune Pancreatitis Can Progress to Chronic Pancreatitis
Some patients with AIP show severe pancreatic calcifications over a long-term course, and those pancreatic stones are a characteristic feature of ordinary chronic pancreatitis, suggesting that AIP could progress to a chronic pancreatitis that fulfills the diagnostic criteria for ordinary chronic pancreatitis.
Serum Levels of IgG4 in Patients with Confirmed Chronic Pancreatitis
It is an interesting matter how many patients with advanced-stage AIP who demonstrated definite chronic pancreatitis symptoms were included with patients having ordinary chronic pancreatitis before the proposal of AIP. We previously reported that more than 60 % of AIP patients maintain high serum IgG4 concentrations even after the clinical symptoms have resolved . Accordingly, if those with advanced-stage AIP are present among cases of confirmed ordinary chronic pancreatitis, these AIP patients might maintain serum IgG4 elevation even at chronic or advanced stages. Thus, we measured serum values of IgG4 in 175 patients with confirmed chronic pancreatitis who had been diagnosed before 1995, the year when the concept of AIP was first proposed. We found high serum IgG4 concentrations in 13 patients with confirmed chronic pancreatitis (7.4 %) (12 men and 1 woman; diagnosis of 9 alcoholic and 4 idiopathic). Among the 13 patients, three had been diagnosed with pancreatic cancer at first, and one had been recently diagnosed with AIP after long-term clinical follow-up. The remaining nine patients showed typical image findings consistent with ordinary chronic pancreatitis, such as pancreatic stones and irregular dilatation of the MPD . This result suggested that an advanced stage of AIP might have been previously included among cases of ordinary chronic pancreatitis and might be regarded as another condition, such as chronic alcoholic pancreatitis.
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Autoimmune Pancreatitis Can Progress to Chronic Pancreatitis that Meets the Revised Japanese Clinical Diagnostic Criteria for Ordinary Chronic Pancreatitis
Our observation that ordinary chronic pancreatitis cases might include a few advanced-stage AIP cases and that some patients with AIP show severe pancreatic calcifications over a long-term course suggested that AIP could progress to chronic pancreatitis that meets the definitive diagnostic criteria for ordinary chronic pancreatitis. We examined whether AIP could transform into chronic pancreatitis that met the revised Japanese clinical diagnostic criteria  and aimed to clarify the susceptibility factors and underlying mechanisms for AIP progressing to confirmed chronic pancreatitis . We enrolled 73 patients with AIP who had been followed for at least 3 years (median follow-up period, 88 months; range, 36–230 months) and found that 16 patients (22 %) were confirmed to have chronic pancreatitis in terms of the revised Japanese clinical diagnostic criteria , including 15 patients with definite chronic pancreatitis and one patient with probable chronic pancreatitis during this study period (Table 25.3). Among the 15 definite cases, major imaging findings were stones in pancreatic ducts in nine (Fig. 25.2a) and multiple or numerous calcifications distributed throughout the entire pancreas in 13 patients (Fig. 25.2b) .
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