Type 2 Autoimmune Pancreatitis in a Young Adult Male: A Diagnostic Challenge.

Type 2 autoimmune pancreatitis (AIP), also known as idiopathic duct-centric pancreatitis, is a rare form of chronic pancreatitis that primarily affects younger individuals and is not associated with IgG4-related disease. Unlike type 1 AIP, serum IgG4 levels are typically normal, making diagnosis challenging and often dependent on a combination of clinical, radiologic, histopathologic, and therapeutic response criteria. We present a 28-year-old male with acute pancreatitis, significant weight loss, and gastrointestinal symptoms. Imaging findings were suggestive of autoimmune pancreatitis. Laboratory evaluation demonstrated elevated total IgG and IgG1 with normal IgG4 levels and a positive anti-smooth muscle antibody. Endoscopic ultrasound-guided pancreatic biopsy revealed nonspecific chronic inflammation and fibrosis, while liver biopsy was consistent with autoimmune hepatitis. In the absence of definitive pancreatic histopathology, the overall clinical presentation was concerning for concomitant type 2 autoimmune pancreatitis.