Gastrointestinal findings in patients with autoimmune pancreatitis

Autoimmune pancreatitis (AIP) is a condition that has been proposed as a clinical entity only fairly recently. Its pathogenesis involves autoimmune mechanisms. Although the radiological findings in patients with AIP have been well evaluated, few studies have focused on the gastrointestinal findings in these patients. The aim of this study was to explore the endoscopic and histological findings in the gastrointestinal tract in patients with autoimmune pancreatitis.

The endoscopic findings in the stomach (n = 10), the duodenum (n = 18), the major duodenal papilla (n = 18), and the colon (n = 5) in 24 patients with AIP were reviewed. These were compared with the results of histological examination of gastric mucosa (n = 13), duodenal mucosa (n = 9), the major duodenal papilla (n = 3), and colonic mucosa (n = 3) in these patients. All these specimens were subjected to immunohistochemical study using anti-IgG4 antibody.

Foci of slightly pale, thickened mucosa with loss of visible vascular pattern were observed in the stomach in four patients and in the colon in two patients on endoscopy. Slight or moderate swelling of the major duodenal papilla was detected in five patients. Slight to moderate lymphoplasmacytic infiltration was observed in the lamina propria of the gastric and colonic mucosa, and of the major duodenal papilla. Heavy infiltration with IgG4-positive plasma cells (>10 cells per high-power field) was observed in the lamina propria of the stomach in seven patients, of the colon in two patients, and of the major duodenal papilla in three patients; this was not observed in the control patients, who had other diseases.

Although there were no specific endoscopic findings in the stomach or colon in patients with autoimmune pancreatitis, foci of slightly pale, thickened mucosa with loss of visible vascular pattern were observed in some cases. This indistinct change seen on endoscopy appears to be due to heavy infiltration with IgG4-positive plasma cells, associated with CD4- or CD8-positive T lymphocytes, in the lamina propria of the gastric or colonic mucosa.