It has been observed that the onset of type 1 diabetes in younger children may be associated with a much stronger influence of DRB1*0301/DRB1*04 and INS I/I genotypes, while the development of type 1 diabetes in older children is especially influenced by the combination of INS I/I and CTLA4 G/G homozygosity. The gene discussed is HLA-DRB1; the disease is type 1 diabetes mellitus.