A novel 19.98 Mb duplication on chromosome Xp22.33-p22.12 was detected by array CGH in a 30 year old man affected by intellectual disability, congenital hypotonia and dysmorphic traits. The duplication encompasses more than 113 known genes. Many of these genes (as neuroligin 4, cyclin-dependent kinase like 5 and others) have already correlated with X-linked intellectual disability and/or neurodevelopmental disorders. Due to the high number of potentially pathogenic genes involved in the reported duplication, we cannot correlate the clinical phenotype to a single gene. Indeed, we suggest that the resulting clinical phenotype may have arisen from the overexpression and consequent perturbation of fine gene dosage.