A rare disorder characterized by mental retardation, spasticity and other variable features. The disorder is inherited in a X-linked manner which means that only males display the full range of symptoms whereas female carriers may have mild or no symptoms. The disorder is caused by a defect on the JARID1C gene on chromosome Xp11.22-p11.21. See also Mental retardation, X-linked, syndromic, due to JARID1C mutation