Objective: The aim of this study was to estimate the number of autoimmune pancreatitis (AIP) patients in Japan and evaluate the influence of steroid therapy on the course of diabetes mellitus (DM) in AIP.
Methods: A total of 2972 departments were randomly selected with hospital stratification throughout Japan. We sent a questionnaire asking the selected departments to report the number of patients who had visited their hospital in 2002 and who fulfilled the diagnostic criteria for AIP set by the Japan Pancreas Society. We then sent a second questionnaire asking for the details of the clinical course of DM, if any, and the treatments used for AIP.
Results: The annual number of AIP in Japan was estimated as approximately 900 (95% confidence interval 670-1100) or 0.71 per 100,000 individuals in the Japanese population. In the second survey, 66.5% of the 167 patients of AIP were reported as being complicated with DM. Among the AIP patients with DM (n = 93), 52% of the patients started to show DM simultaneously with the onset of AIP, and 33% of the patients had DM before the onset of AIP. Following steroid therapy, 55% and 36% of these patient groups showed improvement of DM control, respectively. On the other hand, less than 20% of patients showed newly developed DM or showed exacerbation of DM control after steroid therapy. The older the patients were, the higher were the rates of new development or exacerbation of DM.
Conclusions: These findings indicated that steroid therapy has a beneficial effect on the clinical courses of DM in approximately half of AIP patients. However, it also has negative effect on glucose tolerance in some patients, particularly older patients, and thus, careful observation for involvement of DM should be required in AIP patients treated with steroids.