[Autoimmune pancreatitis - diagnostic consensus]

Area of Science:

• Gastroenterology
• Immunology
• Pathology

Background:

• Autoimmune pancreatitis (AIP) is a distinct pancreatic disease driven by autoimmune processes.
• Two subtypes of AIP exist, sharing histomorphological features but differing in granulocytic epithelial lesions (GEL).
• Subtype 1 is associated with IgG4-related disease, while Subtype 2 links to inflammatory bowel diseases like ulcerative colitis.

Purpose of the Study:

• To delineate the diagnostic criteria for autoimmune pancreatitis.
• To address the challenge of early differential diagnosis between focal AIP and pancreatic head adenocarcinoma.
• To highlight the importance of imaging and histomorphology in diagnosing AIP.

Main Methods:

• Clinical evaluation, biochemical analysis, imaging studies (MRI/CT, MRCP, ERCP in Asia), and histomorphology.
• Utilizing the 2011 consensus criteria for AIP diagnosis.
• Endoscopic ultrasound (EUS) with targeted biopsy under EUS guidance for definitive diagnosis.

Main Results:

• Subtype 1 shows IgG4-positive lesions; Subtype 2 is linked to ulcerative colitis.
• Both AIP subtypes demonstrate a positive response to steroid therapy.
• Consensus criteria (2011) integrate clinical, biochemical, imaging, and histopathological findings.

Conclusions:

• Accurate diagnosis of AIP relies on a combination of diagnostic modalities.
• Distinguishing focal AIP from pancreatic cancer is crucial for appropriate management.
• Steroid responsiveness is a key characteristic for both AIP subtypes.