Abstract : A 17-year-old male presented to our emergency department with the chief complaint of epigastric pain. Serum amylase levels were elevated, and abdominal computed tomography (CT) revealed pancreatic enlargement. The patient was diagnosed with acute pancreatitis. He had no history of alcohol consumption, and blood sampling revealed normal IgG4 levels. Magnetic resonance cholangiopancreatography (MRCP) revealed dilatation of the pancreatic duct at the body-tail. Endoscopic retrograde cholangiopancreatography (ERP) revealed localized stricture of the main pancreatic duct at the head–body transitional area. On endoscopic ultrasound (EUS) , an 18-mm hypoechoic mass was visualized. EUS-guided fine needle aspiration (EUS-FNA) was performed. However, there were no definite findings of autoimmune pancreatitis (AIP) . Lower gastrointestinal endoscopy revealed fine granular mucosa in the rectum, consistent with ulcerative colitis. Based on the diagnosis of a probable type 2 AIP, steroid therapy was initiated. MRCP performed 1 month after treatment showed improvement in the pancreatic duct stricture ; therefore, the patient was considered to be responsive to steroids. Based on the international consensus diagnostic criteria for AIP, the patient was diagnosed with a probable type 2 AIP.
