[Pathogenesis and types of neonatal diabetes].

Studies on pathogenesis of neonatal diabetes may lead to better understanding of pancreatic beta-cell maturation and regulation of insulin secretion. The purpose of this study was to examine the clinical course, immunologic and genetic background of the transient and permanent form of neonatal diabetes. Clinical data (onset and duration of diabetes, C peptide levels, duration of insulin treatment, associated disorders) were collected, islet cell specific antibodies (islet cell antibody and glutamate decarboxylase antibody) were determined and genetic analyses (HLA DQA1-DQB1 typing and microsatellite mapping on chromosome 6) were performed in three patients with permanent and three patients with transient neonatal diabetes. None of the six patients had HLA DQ diabetes susceptibility alleles and most infants were negative for islet cell autoantibodies indicating that no pancreatic islet-cell specific autoimmunity exists in the two forms of neonatal diabetes mellitus. Complete paternal uniparental isodisomy of chromosome 6 has been identified in a transient neonatal diabetes case with macroglossia. The permanent neonatal diabetes cases and the other two cases with transient form did not possess this chromosome anomaly. It is concluded, that none of the two forms neonatal diabetes is of autoimmune origin. They have different genetic background and represent different disease entities. Transient neonatal diabetes is probably caused by alteration of expression of an imprinted gene on chromosome 6 which might play role in fetal growth and pancreatic beta-cell maturation and insulin secretion. Permanent neonatal diabetes is probably a more heterogenous phenotype, the cause of which remains to be clarified in the future.