Autoimmune pancreatitis (AIP) is a recently recognized disease affecting the pancreas. It closely mimics pancreatic cancer in presentation. In fact, pancreatic resections performed for presumed pancreatic cancer have historically played a key role in recognition of this disease entity. Characterized by distinct histological features in the pancreas which has formed the basis of diagnosis for a majority of patients historically, increased recognition of this disease has led to development of diagnostic criteria. In the USA, the HISORt criteria introduced in 2006 has formed the backbone of diagnosing this disease. Recently, international consensus criteria have been developed incorporating experiences and practices from across the world. With increasing experience of this disease, treatment and follow-up strategies have now emerged. The disease is characteristically responsive to steroid treatment. However, relapses are common. Interestingly, two groups of AIP patients were observed with distinct patterns of relapse and corresponding distinctive histological and clinical features. This led to subclassification of AIP into two subtypes: type 1 in which relapses are common and histologically corresponding to lymphoplasmacytic sclerosing pancreatitis (LPSP) with IgG4 positivity and type 2 in which relapses are rare and histologically characterized by granulocyte epithelial lesions (GELs). Long-term follow-up data have now established that despite relapses, AIP is a benign disease which does not affect overall survival.
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