Genetic dispositions to autoimmune insulitis diabetes mellitus type 1 and LADA syndrom are based mainly on polymorphisms of HLA DR, DQ, promotor region of the insulin gene, and the gene of cytotoxic T-lymphocyte antigen 4. Any other mutations in insulin gene itself are very rare (Chicago, Los Angeles, Kyoto). A separate group of diabetes mellitus is MODY 1 to 7, where mutations in the glucokinase gene or in the hepatic nuclear transcription factors genes are involved. Special attention is required for mutations in mitochondrial DNA causing MIDM (eg. mutation in Leu-tRNA gene). Diabetes mellitus type 2 is obviously dependent on the life style, but still 90 % concordance in homozygous twins is evident. Genetic dispositions to diabetes mellitus include also mutations in HFE gene (hemochromatosis) and CFTR gene (cystic fibrosis). There are at least 14 genes known up to date responsible for monogenic form of diabetes mellitus.

        Key words: diabetes melllitus, gene mutation, MODY, autoimmunity, polymorphism, IPEX, APECED.