Autoimmune pancreatitis characterized by predominant CD8+ T lymphocyte infiltration

Autoimmune pancreatitis (AIP) is a rare form of pancreatitis characterized by prominent lymphocyte infiltration and pancreatic fibrosis resulting in organ dysfunction. The pathogenesis and pathology of AIP remain unknown. A 64-year-old Chinese man presented with symptoms and signs of bile duct obstruction diffuse enlargement of the head of pancreas, elevated IgG levels, and negative autoimmune antibody responses. A pylorus-preserving pancreatoduodenectomy was performed and a pancreatic tumor was suspected. However, periductal lymphoplasmacytic infiltration and fibrosis were found in the head of pancreas and nearby organs instead of tumor cells. Four months after surgery, the patient was readmitted because of reoccurrence of severe jaundice and sustained abdominal distension. Prednisone 30 mg/d was administered orally as an AIP was suspected. One and a half months later, the symptoms of the patient disappeared, and globulin, aminotransferase and bilirubin levels decreased significantly. Over a 9-mo follow-up period, the dose of prednisone was gradually decreased to 10 mg/d and the patient remained in good condition. We further demonstrated dominant CD3+/CD8+ populations, CD20+ cells and a few CD4+ cells in the pancreatic parenchyma, duodenum and gallbladder wall by immunohistochemical assay. This AIP case presented with significant CD8+ T lymphocyte infiltration in the pancreas and extra-pancreatic lesions, indicating that this cell population may be more important in mediating AIP pathogenesis than previously known and that AIP might be a poorly defined autoimmune disease with heterogeneous pathogenesis.