The genetics of diabetes mellitus in man.

The genetics of diabetes mellitus in man has been reviewed. The evidence for genetic heterogeneity on clinical, biochemical and HLA (histocompatibility leukocyte antigens) data is presented. An attempt is made to interpret the meaning of the associations of the disease and certain HLA antigens and the complement factor, properdin in populations and in families. The population data can be best explained by the linkage disequilibrium hypothesis requiring tight linkage between the DS (diabetes susceptibility) locus and those in the MHC (major histocompatibility complex). Linkage between the DS locus and MHC from family data is estimated to be about 14%, which is not likely tight enough to be compatible with the population data; and a one locus or one allele hypothesis and genetic heterogeneity is postulated as the best explanation of the incompatibility between population and family data. It is still impossible to precisely define the exact genetic hypothesis for diabetes in man.