Analysis of pancreatic endocrine function in patients with IgG4-related diseases, in whom autoimmune pancreatitis was ruled out by diagnostic imaging.

IgG4-related disease (IgG4RD) is a newly recognized systemic disease characterized by the elevation of serum IgG4 levels and abundant IgG4-positive plasma cell infiltration into the involved organs. Few data exist regarding the relationship between diabetes or glucose intolerance and IgG4RD in the absence of obvious type 1 autoimmune pancreatitis (AIP). Therefore, we are characterizing pancreatic endocrine function in IgG4RD patients with no signs of type 1 AIP. 28 patients (12 men, mean age 62.1 years old) were diagnosed as having IgG4RD from serum IgG4 levels, histopathology and images. Diagnostic imaging ruled out obvious type 1AIP. We used 75g oral glucose tolerance tests (OGTT) and arginine tolerance tests (ATT) to evaluate pancreatic endocrine function. Patients' serum IgG4 and HbA1c levels were 603±437 mg/dL and 6.6±1.0%, respectively. The results of OGTT on 23 patients showed that 12 patients had diabetes, 4 had impaired glucose tolerance, and 7 had normal glucose tolerance. Interestingly, insulin secretion was preserved in most of the patients, even in diabetic patients, on OGTT and ATT. Glucagon hyperreactivity was observed in 10 of the 19 patients who underwent ATT. Twenty-three patients were treated for IgG4RD with glucocorticoids. Their HbA1c levels were significantly elevated during the first six months of treatment, but improved after twelve months in parallel with glucocorticoid therapy. These results demonstrate the high frequency of pancreatic endocrine dysfunction in IgG4RD even when there is no indication of AIP, thus revealing that pancreatic endocrine dysfunction frequently occurs in IgG4RD without obvious type 1 AIP.