Etiology pathogenesis Monozygotic twins-IDDM(30-50%) .HLA DR3/DR4DDM(70%) 2. Genetics. Aspartic acid on position 57 of HLA-DQ B chain protective effect for TIDM arginine on position 52 of HLA-dQ a chain increases susceptibility to DMEtiology & pathogenesis 2.Genetics •Monozygotic twins→IDDM (30－50％) •HLA DR3/DR4 →IDDM (70%) •Aspartic acid on position 57 of HLA-DQ  chain protective effect for T1DM •Arginine on position 52 of HLA-DQ  chain increases susceptibility to DM