Autoimmune pancreatitis: Cornerstones and future perspectives

Abstract

Autoimmune pancreatitis (AIP) is an autoimmune subtype of chronic pancreatitis resulting from the aberrant immune response against the pancreas, leading to inflammation and fibrosis. Although AIP is rare, its incidence is increasing and is often misdiagnosed as other pancreatic diseases. AIP is commonly classified into two types. Type 1 AIP (AIP-1) is typically associated with elevated serum immunoglobulin G4 (IgG4) levels and systemic manifestations, while type 2 AIP is typically a more localized form of the disease, and may coexist with other autoimmune disorders, especially inflammatory bowel diseases. Additionally, there is emerging recognition of a third type (type 3 AIP), which refers to immunotherapy-triggered AIP, although this classification is still gaining acceptance in medical literature. The clinical manifestations of AIP mainly include painless jaundice and weight loss. Elevated serum IgG4 levels are particularly characteristic of AIP-1. Diagnosis relies on a combination of clinical, laboratory, radiological, and histological findings, given the similarity of AIP symptoms to other pancreatic disorders. The mainstay of treatment for AIP is steroid therapy, which is effective in most cases. Severe cases might require additional imm-unosuppressive agents. This review aims to summarize the current knowledge of AIP, encompassing its epidemiology, etiology, clinical presentation, diagnosis, and treatment options. We also address the challenges and controversies in diagnosing and treating AIP, such as distinguishing it from pancreatic cancer and managing long-term treatment, highlighting the need for increased awareness and knowledge of this complex disease.

Keywords: Autoimmunity; Pancreatitis; Autoimmune pancreatitis; Immunoglobulin G4; Steroids; Relapse

Core Tip: Autoimmune pancreatitis (AIP) is rare and often misdiagnosed. The lymphoplasmacytic sclerosing form, type 1 AIP (AIP-1), represents the pancreatic manifestation of immunoglobulin G4-related disease, while the idiopathic ductal centric form, type 2 AIP (AIP-2), is often associated with inflammatory bowel disease. AIP-1 presents with obstructive jaundice or abnormalities in exocrine and endocrine pancreatic function; AIP-2 usually shows abdominal pain and acute pancreatitis. The atypical mass-forming abnormality of the pancreas implies the need to histologically distinguish AIP form pancreatic ductal adenocarcinoma. Steroids are the first-line therapy for both AIP-1 and AIP-2, rituximab is a good alternative for AIP-1. Given the high relapse rate, long-term maintenance therapy is recommended. Scientific efforts are focusing on target therapies.