Misdiagnosis and delayed diagnosis of atypical autoimmune pancreatitis: Experience from clinical cases.

Autoimmune pancreatitis (AIP) is a fibro-inflammatory disease characterized by inflammation and fibrosis of the pancreas. It is a systemic disease that can affect multiple organs, including the bile ducts, kidneys, lungs, and other organs. However, due to its complex presentation, AIP is often challenging to diagnose, and misdiagnosis with pancreatic tumors can occur. In our study, we reviewed three cases of atypical AIP where patients had normal serum IgG4 levels, leading to initial misdiagnosis with pancreatic tumors. Delayed diagnosis resulted in irreversible pathologies such as retroperitoneal fibrosis. All three patients had bile duct involvement, and imaging findings were similar to those of tumors, further complicating the diagnosis. The correct diagnosis was confirmed only after diagnostic therapy. Our study aims to raise awareness of atypical AIP and improve diagnostic efficiency by analyzing the clinical characteristics of these patients.