[Autoimmune pancreatitis: new concepts of an often overlooked disease].

Autoimmune pancreatitis is characterized by a lympho-plasmacytic infiltrate centred around the pancreatic ducts along with venulitis; it can produce a mass-like fibroinflammatory lesion and often simulates pancreatic malignancy or chronic pancreatitis of other types. This may lead to unnecessary surgical interventions. Patients, who are usually over 40 years of age, show 1) mild unspecific abdominal pain, 2) increased serum immunoglobulins (specifically IgG4) and autoantibodies, and 3) diffuse or focal enlargement of the pancreas with pancreatic strictures and sometimes jaundice due to biliary obstruction (detectable by US, CT, MRI, ERCP and/or endoscopic ultrasound (EUS)). The diagnosis can be strongly supported by EUS- or US-guided biopsies showing typical histological changes and specific indirect immunohistochemistry with the patient's serum or a steroid trial showing often a dramatic decrease of pathological findings within weeks.