Autoimmune Pancreatitis
Atsushi Masamune，Atsushi Kanno，and Tooru Shimosegawa
Abbreviations
AIP Autoimmune pancreatitis
CP Chronic pancreatitis
CT Computed tomography
ERP Endoscopic retrograde pancreatography
EUS-FNA Endoscopic ultrasound-guided fine needle aspiration
GEL Granulocytic epithelial lesion
ICDC International Consensus Diagnostic Criteria(https://www.daowen.com)
IDCP Idiopathic duct-centric chronic pancreatitis Ig，immunoglobulin
LPSP Lymphoplasmacytic sclerosing pancreatitis
miRNA microRNA
MPD Main pancreatic duct
NOS Not otherwise specified
OOI Other organ involvement
PSL Prednisolone
Abstract Autoimmune pancreatitis（AIP）is a relatively rare type of pancreatitis with a hypothesized autoimmune mechanism.AIP has several distinct clinical，serological，and morphological characteristics.Diffuse enlargement of the pancreas and irregular narrowing of the main pancreatic duct are typical imaging findings of AIP.AIP frequently presents with obstructive jaundice and increased serum immunoglobulin G4（IgG4）.AIP has two distinct phenotypes:type 1 and type 2 AIP.Histologically，lymphoplasmacytic sclerosing pancreatitis is characteristic of type 1 AIP，whereas idiopathic duct-centric chronic pancreatitis with granulocytic epithelial lesions is characteristic of type 2 AIP.Type 1 AIP is now regarded as a pancreatic manifestation of systemic IgG4-related disease and is often associated with extra-pancreatic lesions such as IgG4-related sclerosing cholangitis.AIP can be diagnosed according to the International Consensus Diagnostic Criteria based on pancreatic parenchymal imaging，ductal imaging，serology，other organ involvement，histology，and response to steroids（optional）.AIP patients respond dramatically to corticosteroid therapy and corticosteroid has been established as a standard therapy for the treatment of AIP patients.The requirement of maintenance therapy has been controversial.For patients who are either intolerant of corticosteroids or have multiple relapses，there are other treatment options，including corticosteroid-sparing immunomodulators and B-cell depletion therapy using rituximab，which might be alternative treatment options.Overall，the prognosis of AlP is good.It is controversial whether AIP patients have an increased risk for cancer.Obviously，long-term follow-up will be required to clarify the outcomes of AIP patients.