Autoimmune pancreatitis

Abstract

Autoimmune pancreatitis (AIP) is a rare, distinct and increasingly recognized form of pancreatitis which has autoimmune features. The international consensus diagnostic criteria (ICDC) for AIP recently described two subtypes; type 1[lymphoplasmacytic sclerosing pancreatitis (LPSP)] and type 2 [idiopathic duct-centric pancreatitis (IDCP) or AIP with granulocytic epithelial lesion (GEL)]. Type 1 is the more common form of the disease worldwide and current understanding suggests that it is a pancreatic manifestation of immunoglobulin G4-related disease (IgG4-RD). In contrast, type 2 AIP is a pancreasspecific disease not associated with IgG4 and mostly without the overt extra-pancreatic organ involvement seen in type 1. The pathogenesis of AIP is not completely understood and its clinical presentation is nonspecific. It shares overlapping features with more sinister pathologies such as cancer of the pancreas, which continues to pose a diagnostic challenge for clinicians. The diagnostic criteria requires a variable combination of histopathological, imaging and serological features in the presence of typical extrapancreatic lesions and a predictable response to steroids.

Clinical-Pathological Conference Series from the Medical University of Graz

“…In the past, AIP has been described by various terms including chronic inflammatory sclerosis of the pancreas, chronic sclerosing pancreatitis, non-alcoholic duct-destructive chronic pancreatitis, lymphoplasmacytic sclerosing pancreatitis, idiopathic tumefactive chronic pancreatitis and idiopathic duct-centric chronic pancreatitis [ 27 ]. With an estimated prevalence of <1–2.2 per 100,000 in the general population, AIP is a rare disorder [ 28 , 29 ].…”

“…In type 1 AIP males are more often affected than females (3:1; [ 21 ]), but there is no gender predilection documented for type 2 [ 33 ]. While type 2 AIP is a pancreas-specific disease mostly without extrapancreatic organ involvement and negative serology for IgG4 and autoantibodies, type 1 AIP is suggested to be a pancreatic manifestation of an IgG4-related disease characterized by systemic inflammation of unknown origin [ 27 ]. Despite the frequent association with elevated levels of IgG4 in serum and plasma cells in tissue, the role of IgG4 in AIP remains unclear.…”

“…The clinical presentation of AIP is non-specific, sharing overlapping features with other diseases such as pancreatic cancer. Diagnosis requires a variable combination of histopathological, imaging and serological features in the presence of typical extrapancreatic lesions and a predictable response to steroids [ 27 ]. According to the ICDC, rapid response (≤2 weeks) to steroids is a diagnostic criterion for AIP (Table 2 ), but in some cases response may even take 1–4 months [ 49 , 50 ].…”

“…in a patient with IgG4 positive AIP type 1 [ 60 ]. General evidence in support of the association between extrapancreatic manifestations and AIP include (1) shared characteristic histopathological findings of lymphoplasmacytic infiltration, IgG4-positive plasma cell infiltration, obliterative phlebitis and storiform fibrosis, (2) frequent co-existence or occurrence, (III) predictably favorable response to steroids and (4) differentiation from the lesion of the corresponding organ [ 27 ]. The immunopathological mechanism between AIP and cutaneous purpuric leukocytoclastic vasculitis is not clear but an increased deposition of immune complexes formed in response to the underlying systemic disease is a possible explanation; however, leukocytoclastic vasculitis may even occur without demonstrable histological immunoreactivity [ 61 ].…”

Present status and perspectives of endosonography 2017 in gastroenterology

“…Autoimmune pancreatitis constitutes the majority of cases in immunoglobulin G4 (IgG4)-related diseases [ 52 ]. The disease is rarely confined to the pancreas and is most often associated with other immune-related changes, such as involvement of the extrahepatic bile duct or retroperitoneum [ 53 ].…”