In 2005, Van Esch and colleagues documented four families with a history of XLID and using array comparative genomic hybridization (array-CGH) and quantitative PCR (qPCR), found 13 males with a < 450 kb duplication of the Xq28 region including MECP2 exhibiting a form of intellectual disability associated with progressive spasticity [2]. Here, MECP2 is linked to Intellectual disability.