In 4 families with X-linked intellectual disabilities and a copy number gain of an identical 0.3 Mb region in chromosome band Xq28 including 19 annotated genes including FLNA and GDI1 (an X-linked mental retardation gene) but not MECP2, affected patients presented with hypotonia, severely delayed psychomotor development, mild ataxic gait, strabismus or nystagmus but no other cerebellar signs. The gene discussed is MECP2; the disease is Intellectual disability.