Objectives: Autoimmune pancreatitis (AIP) and its extrapancreatic lesions seem to be clinical manifestations of organs involved in IgG4-related systemic disease. To clarify whether the stomach is a target organ, gastric function was evaluated in patients with AIP.
Methods: In 6 patients with AIP, gastric emptying was assessed by Carbon 13 (¹³C) acetate breath test before and after steroid therapy. Based on 4-hour breath samples, the half ¹³CO₂ excretion time (T(1/2)) and the time of maximal excretion (T(max)) were calculated as gastric emptying parameters. Data of 20 healthy volunteers were used as controls. The number of IgG4-positive plasma cells in gastrofiberscopic biopsy specimens was counted before and after steroid therapy.
Results: Both T(1/2) and T(max) in patients with AIP decreased significantly after steroid therapy (T(1/2): 1.89 ± 0.21 hours vs 1.69 ± 0.15 hours, P = 0.046; and T(max): 1.1 ± 0.2 hours vs 0.96 ± 0.2 hours, P = 0.027), and became similar to those of the controls (T(1/2): 1.69 ± 0.32 hours and T(max): 0.98 ± 0.2 hour). The number of IgG4-positive plasma cells infiltrating the gastric mucosa decreased after steroid therapy.
Conclusions: Gastric emptying was impaired in patients with AIP and improved to the reference range after steroid therapy. The stomach may be a target organ of IgG4-related systemic disease.