GAD Ab positive T1DM has been associated with the HLA class II haplotypes DQA1*05:01-DQB1*02:01- DRB1*03:01 (DQ2-DR3) and DQA1*03:01-DQB1*03:02- DRB1*04 (DQ3-DR4) [89,90], the DQ2-DR3 haplotype being also related to autoimmune thyroiditis [91]. The gene discussed is GAD1; the disease is type 1 diabetes mellitus.