Recent Advances in Autoimmune Pancreatitis

Area of Science:

• Gastroenterology and Immunology
• Pancreatic Diseases
• Autoimmune Disorders

Background:

• Autoimmune pancreatitis (AIP) presents with obstructive jaundice, lymphoplasmacytic infiltrate, and responds to steroids.
• Two distinct types, type 1 and type 2 AIP, share features but differ in demographics, presentation, and natural history.
• Type 1 AIP is the pancreatic manifestation of immunoglobulin G4-related disease (IgG4-RD).

Purpose of the Study:

• To propose distinct nomenclature for type 1 AIP and type 2 AIP, renaming the latter to idiopathic duct-centric chronic pancreatitis (IDCP).
• To differentiate the pathogenesis, clinical features, and treatment strategies for type 1 AIP and IDCP.
• To highlight the role of B cells in AIP pathogenesis and the effectiveness of B-cell depletion therapy.

Main Methods:

• Review and analysis of clinical, histological, and therapeutic data for type 1 and type 2 AIP.
• Examination of the association between AIP and immunoglobulin G4-related disease (IgG4-RD).
• Evaluation of treatment responses, including corticosteroids, immunomodulators, and rituximab.

Main Results:

• Type 1 AIP is associated with IgG4-RD, while type 2 AIP (IDCP) is less understood and linked to inflammatory bowel disease in ~25% of cases.
• B-cell depletion therapy with rituximab is effective for AIP/IgG4-RD, indicating a crucial role for B cells.
• Both AIP and IDCP respond to corticosteroids, but AIP has common relapses requiring maintenance therapy (azathioprine, 6-mercaptopurine, mycophenolate mofetil, or rituximab), whereas IDCP relapses are rare.

Conclusions:

• Renaming type 2 AIP to idiopathic duct-centric chronic pancreatitis (IDCP) clarifies its distinct disease status.
• Understanding the distinct roles of B cells in AIP and the association with IgG4-RD guides therapeutic strategies.
• Long-term survival is excellent for both AIP and IDCP, though management differs due to relapse rates.