Intellectual Developmental Disorder, X-Linked 99, also known as mental retardation, x-linked 99, is related to intellectual developmental disorder, x-linked 99, syndromic, female-restricted and female-restricted syndromic x-linked intellectual disability 99. An important gene associated with Intellectual Developmental Disorder, X-Linked 99 is USP9X (Ubiquitin Specific Peptidase 9 X-Linked). Affiliated tissues include kidney and brain, and related phenotypes are intellectual disability and hypotonia