Misdiagnosis of autoimmune pancreatitis: a caution to clinicians.

Autoimmune pancreatitis (AIP) is a chronic inflammatory disease of the pancreas that is increasingly encountered worldwide. It has generated considerable interest, in part because the inflammatory process usually responds dramatically to corticosteroid therapy. The most common presentation mimics that of pancreatic cancer; thus, a correct diagnosis of AIP can avoid major surgery. However, the diagnosis is challenging, because its incidence is far lower than that of the diseases it mimics and there is no single diagnostic clinical feature or test that can identify the full spectrum of AIP. Therefore, we are increasingly encountering patients misdiagnosed as having AIP. The misdiagnosis typically occurs in three scenarios: (i) treatment of pancreatic or biliary malignancy with corticosteroids and/or immunomodulators, (ii) treatment of chronic abdominal pain with corticosteroids and/or immunomodulators, or (iii) performance of operative resection for autoimmune disease. Our purpose is to highlight this growing clinical problem and to reinforce the use of published guidelines for the diagnosis and management of AIP.