Mumps with laboratory signs of subclinical pancreatitis may cause a disturbed beta-cell function.

Mumps epidemics are followed by sporadic cases of insulin dependent diabetes mellitus (IDDM). We have studied beta-cell function in 11 subjects who had had a mumps infection. They had no clinical pancreatitis but were selected as they had abnormal pancreas iso-amylase values and/or glucosuria during the mumps virus infection. At the follow-up some years later the subjects were healthy. A few HbA1-values were noted in the upper part of the normal range. Total serum insulin values were normal, but the C-peptide values were low at first follow-up 1-3 years after infection in all but two patients. These values increased in 4/7 patients during the follow-up period but were subnormal in five subjects still 3-6 years after the infection. All five patients had HLA-DR 3 and/or 4. In 7 out of 11 patients islet cell surface antibodies could be demonstrated. Our results indicate that subclinical mumps pancreatitis may initiate a reaction towards the beta-cells recognized as subnormal C-peptide levels several years later in certain patients. This might contribute to manifest IDDM many years after infection.