Autoimmune Pancreatitis: The Emerging Role of Serologic Biomarkers

Abstract

Autoimmune pancreatitis (AIP) is a relatively new clinical entity whose acceptance as a distinct systemic disease has grown in the last decade with the emergence of improved diagnostic criteria and management options. AIP has characteristic clinical, radiological, serological, and histological features (1). A subset of patients with AIP develops fulminant type 1 diabetes (2,3). The pathogenesis remains unresolved, but immune-mediated mechanisms that compromise endocrine and exocrine pancreatic function appear to be involved. Characteristic imaging criteria include pancreatic enlargement with an irregular, narrow pancreatic duct. The presence of diffuse swelling and “halo” features on computed tomography appear to be predictors of a favorable response to treatment with corticosteroids, whereas the presence of ductal strictures and focal swelling may predict suboptimal response to corticosteroids, the current first-line treatment (4). Cases of AIP with focal enlargement, distinct mass, normal pancreas, and focal acute pancreatitis have been observed as well as involvement of other organs, such as intrahepatic biliary strictures. Serum IgG or IgG4 levels are elevated in a majority of cases. Histologic features include the presence of lymphoplasmacytic sclerosing pancreatitis and infiltration of tissues with IgG4-positive cells (5) (Fig. 1). It is important to rule out pancreatobiliary cancer because of overlap in imaging criteria and other clinical features. The identification of a sensitive and specific biomarker for autoimmune pancreatitis detection of autoantibody responses directed to amylase α-2A represents a significant advance for the diagnosis and management of this condition. While the pathogenesis of AIP and fulminant type 1 diabetes remains to be elucidated, both entities appear to share pancreatic autoimmune manifestations. A biphasic mechanism has been proposed recently consisting of “induction” and “progression” stages (6). An initial induction response to self-antigens and molecular mimicry is mediated by decreased naive regulatory T-cells, and T-helper cells release proinflammatory cytokines. In the chronic phase, …