**6. Late prognosis: progression to chronic pancreatitis**

AIP has been considered as a subclass of chronic pancreatitis (CP). There is no doubt that autoimmune factors can have some importance of the pathogenesis of CP and also in some cases of recurrent acute pancreatitis (RAP). There is also a possibility that the idiopathic advanced CP in several cases can be the late consequence of unrecognized and untreated AIP. However, clinical and epidemiological characteristics; morphological alterations in CT, MR, and EUS; images and histology are all quite different when compared to CP [35]. In addition, CP is a progressive damage to the pancreas, while AIP is a reversible disease after an adequate treatment. There are contradictory observations in the literature about the longterm outcome of AIP [36–38]. When we evaluate the published observations, we must be cautious, and we have to remember that AIP was definitively described only in 1995; it means that follow-up of patients for a period longer than 20 years is lacking. Biliary stenting by ERCP [39] and significant focal stenosis of the main pancreatic duct [40] were found as risk factors for formation of pancreatic stones and progression to CP. Exocrine and endocrine insufficiencies were described in a significant number of patients [41], even without detectable changes of advanced pancreatic disease. However, pancreatic enzyme replacement therapy has not been routinely used even in these cases. Our limited experiences are different: while 11 of our 74 patients had diabetes, clinically overt exocrine insufficiency was observed only in 2 of them [18], requiring oral pancreatic enzyme replacement therapy. We can find similar doubts in the literature about the risk of malignancy: higher incidence of pancreatic and extrapancreatic cancer was described by some authors [42] but not confirmed by others [43]. We did not observe malignant disease in our cohort of patients.

The possibility of AIP to PC requires longer observations. However, we insist that AIP in our opinion is not a simple subclass of CP. The differences are as strong as or even stronger than in the case of obstructive pancreatitis. Both of these entities can be reversible with an adequate timely treatment, and probably both of them can progress to CP if their cause persists unresolved [44]. If it is true, it underlines even more the importance of the early diagnosis and proper treatment.
