Serum and histological IgG4-negative type 1 autoimmune pancreatitis

A 66-year-old man who was on oral medication for type 2 diabetes experienced a rapid decline in glycemic control (increase in glycosylated hemoglobin level from 7.7 to 10.2% over 3 months). Abdominal ultrasonography revealed a 20-mm hypoechoic mass in the pancreatic tail. Serum tumor marker carbohydrate antigen 19–9 and DUPAN2 levels were within the respective normal ranges; serum IgG4 level was also normal at 21.8 mg/dL. Abdominal contrast...