Clinicopathological features of autoimmune pancreatitis in relation to elevation of serum IgG4

Objectives: To examine the clinicopathological differences between patients with autoimmune pancreatitis in relation to presence or absence of elevated serum IgG4 concentrations. Methods: We divided 21 patients with autoimmune pancreatitis into 2 groups on the basis of serum IgG4 concentration: elevated (>135 mg/dL) and low. The number of IgG4-immunoreactive plasma cells in the pancreas, bile duct, gallbladder, gastric mucosa, and abdominal lymph nodes was examined. Results: Serum IgG4 concentrations were elevated in 14 patients (150-1890 mg/dL). No significant differences in age and sex, frequencies of pancreatic swelling, biliary stenosis, presence of auto-antibodies, and salivary glands enlargement were identified between the 2 groups. Abdominal lymphadenopathy was detected at laparotomy more frequently in patients with high serum IgG4 (P < 0.05). Although no difference in number of IgG4-positive plasma cells infiltrating the pancreas was observed between the 2 groups, patients with elevated IgG4 tended to exhibit more of these cells infiltrating the wall of the bile duct and abdominal lymph nodes, significantly more of these cells infiltrating the gastric mucosa (P < 0.01). Conclusion: IgG4-related phenomena occurred in various organs of patients with autoimmune pancreatitis associated with elevated IgG4, whereas these phenomena tended to be rather confined to the pancreas in patients with low serum IgG4.