Brain and beyond the brainthe biological profile of Down syndrome

Down syndrome (DS) is the most frequent genetic disorder associated with intellectual disability. It results from a a triplicate chromosome 21.The phenotype can be variable in severity, on the basis of allelic composition of chromosome 21 genes and of the interaction with environment and expression of genes that are not located on chromosome 21. Dysregulation of the immune system is one characteristic pathological feature of the DS and likely contributes to increased susceptibility to viral or bacterial infections, autoimmune diseases, and haematologic maligancies. Chromosome 21 contains the interferon cytokine receptors clustrer of genes that are structurally and functionally related. Precocious Alzheimer manifestations may be relataed to an overproduction of beta-amyloid related to the presence of an extra gene for this protein. A better understanding of genotype-phenotype correlation in DS may provide a rationale for more effective thrapeutic strategies in DS as well as in karyotypicolly normal individuals with Alzheimer disease.