Findings on CDK5R1 deletion in patients with NF1 microdeletion syndrome showing mental retardation [17,18] and the recently reported CDK5R1 mutations in non-syndromic mental retardation patients [19], pinpoint the gene as a candidate for mental retardation susceptibility in NF1 microdeletion syndrome and in a subgroup of non-syndromic mental retarded patients. Here, NF1 is linked to Intellectual disability.