Serum IgG4 levels and extrapancreatic lesions in autoimmune pancreatitis.

Objective: Serum IgG4 levels are frequently elevated in patients with autoimmune pancreatitis (AIP). AIP is sometimes associated with various extrapancreatic lesions. This study examined whether there is a correlation between serum IgG4 levels and associated extrapancreatic lesions in AIP patients.

Methods: Serum IgG4 levels were measured in 40 AIP patients before therapy. In these patients, four associated extrapancreatic lesions (sclerosing cholangitis, sclerosing cholecystitis, sclerosing sialadenitis, and retroperitoneal fibrosis) and clinical factors, such as age, sex ratio, enlargement of the pancreas, and initial symptoms, were retrospectively assessed.

Results: The mean serum IgG4 level of the 40 AIP patients was 411+/-448 mg/dl. On the basis of the receiver operator characteristic curve data, the optimal cutoff value for the serum IgG4 to distinguish between AIP patients with and without extrapancreatic lesions was 220 mg/dl; 18 (78%) of 23 patients whose serum IgG4 was more than or equal to 220 mg/dl had extrapancreatic lesions, whereas four (24%) of 17 patients whose serum IgG4 was less than 220 mg/dl had extrapancreatic lesions (P=0.0011). No significant differences between the two groups in age, sex, the frequency of pancreatic enlargement or obstructive jaundice, and associated sialadenitis, retroperitoneal fibrosis, and diabetes mellitus were identified. Sclerosing cholangitis and cholecystitis were more frequent in patients with serum IgG4 levels of more than or equal to 220 mg/dl than in those with a lower serum IgG4 level (P=0.0002 and 0.0204, respectively). The number of associated extrapancreatic lesions was significantly greater in patients with a high-serum IgG4 level.

Conclusion: AIP patients with serum IgG4 levels of more than or equal to 220 mg/dl frequently have extrapancreatic lesions.