This study aimed to determine calcineurin activity, oxidative and glycosylation damage in children with Down Syndorome and to correlate these results with the degree of abnormalities of Down Syndorome patients . It was conducted on 52 cases (age range 2-5) with Down Syndorome compared to 20 control cases. In our study, there's a significant decrease in calcineurin activity and an increase in oxidative and glycosylation damage in Down Syndrome patients compared to controls.