We studied the CTLA-4 (+49 A/G) polymorphism because it has been the most widely analyzed variant in different ethnic groups, and still with inconsistent findings.16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41Furthermore, this is the first study investigated the effect of +49A/G polymorphism among Sudanese children with T1DM, bearing in mind a recent data investigated this polymorphism among Sudanese adults with T1DM.9 The gene discussed is CTLA4; the disease is type 1 diabetes mellitus.