Polymorphism of HLA and insulin gene is correlated to type I diabetes.

A polymorphic locus flanking the 5'-end of the insulin gene was studied by means of the recombinant DNA technique in 62 diabetic and nondiabetic subjects. The small allele predominantly was found with the following frequencies: 28 insulin-dependent diabetics 0.89; 6 probands of a family with one type I diabetic member 0.92; 10 patients with a non-insulin-dependent diabetes mellitus 0.55; 18 control probands (normal glucose tolerance) 0.64. --Because of the relatively high number of all probands with the small allele we assume that the presence of this allele on both chromosomes increases the susceptibility but is not sufficient for the onset of an insulin-dependent diabetes mellitus. By a correlation of the polymorphic region of the insulin gene with other DNA regions (in particular with the major histocompatibility complex) the susceptibility may be further increased. Therefore, the HLA-DR gene polymorphism of type I diabetes is of interest.