• Endoscopic retrograde cholangio pancreatography
• IgG4
• autoimmune pancreatitis
• cholangitis
• differential diagnosis
• autoimmune disease
• imaging
• immunoregulation
• pancreatitis

Autoimmune pancreatitis (AIP) is a puzzling disease. Although its cardinal features were first reported in Europe,1 it seemed, for a long time an Asian phenomenon which many Western clinicians felt they could largely ignore.2 3 As more case series were reported from Europe and America it became increasingly clear that AIP affects patients from many ethnic backgrounds. AIP shares features with two other disorders of the pancreas from which a distinction is critical and determines appropriate treatment. The first is chronic pancreatitis of either the environmentally induced (alcohol, tobacco smoke) or the hereditary variety.4–6 The most important difference in terms of treatment, prognosis and, to a lesser degree, diagnosis is that AIP rapidly responds to the administration of steroids7 and other varieties of pancreatitis do not.

Reports from Japan suggesting that AIP can be distinguished from chronic pancreatitis by serological markers alone, most prominently serum IgG4 levels,8 were greeted with great enthusiasm. Unfortunately, clinical chemistry was quickly found to be much less reliable in Caucasian patients.9 The reason behind this difference lies in two subtypes of AIP with different prevalence in Europe and Asia. The first subtype, and by far the most common in Asia, has recently been termed lymphoplasmacytic sclerosing pancreatitis (LPSP or type I AIP) according to its histological features.10 It is commonly associated with immunological changes such as elevated IgG4 serum levels or various autoantibodies of lesser diagnostic value. A second disease variety named idiopathic duct-centric pancreatitis (IDCP or type II AIP), that barely exists in Japan, accounts for a significant number of Caucasian patients, displays often none of the immunological changes and is characterised histologically by granulocytic epithelial lesions. …