Autoimmune pancreatitis type 2

Autoimmune pancreatitis type 2 (AIP type 2), also known as idiopathic duct-centric pancreatitis (IDCP) or granulocytic epithelial lesion (GEL)-positive pancreatitis, is a rare inflammatory disorder of the pancreas. Unlike autoimmune pancreatitis type 1, which is part of the systemic IgG4-related disease spectrum, AIP type 2 is a pancreas-specific condition characterized by neutrophilic infiltration of the pancreatic duct epithelium (granulocytic epithelial lesions) without elevated serum IgG4 levels. It primarily affects the exocrine pancreas, leading to pancreatic enlargement, ductal narrowing, and impaired pancreatic function. Patients typically present with obstructive jaundice, abdominal pain, and acute pancreatitis. AIP type 2 tends to affect younger individuals compared to type 1, often presenting in the fourth to fifth decade of life, and affects males and females equally. A notable clinical association exists with inflammatory bowel disease (IBD), particularly ulcerative colitis, which is found in a significant proportion of patients. Unlike type 1, AIP type 2 does not typically involve other organs and serum autoantibody markers are generally absent, making diagnosis more challenging and often requiring histological confirmation through biopsy or surgical resection specimens. Treatment for AIP type 2 centers on corticosteroid therapy, which is highly effective in inducing remission. Most patients respond well to an initial course of oral corticosteroids such as prednisone, with gradual tapering over several weeks. A key advantage of AIP type 2 over type 1 is its significantly lower relapse rate; recurrence after successful steroid treatment is uncommon. In cases where the disease mimics pancreatic cancer on imaging, accurate diagnosis is critical to avoid unnecessary surgical resection. Long-term prognosis is generally favorable with appropriate treatment, though monitoring for associated inflammatory bowel disease is recommended.

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