The term 'X-linked mental retardation-hypotonic facies syndrome' comprises several syndromes previously reported separately. These include Carpenter-Waziri, Holmes-Gang, and Smith-Fineman-Myers syndromes as well as 1 family with X-linked mental retardation with spastic paraplegia. All these syndromes were found to be caused by mutation in the XH2 gene and are characterized primarily by severe mental retardation, dysmorphic facies, and a highly skewed X-inactivation pattern in carrier women. Other more variable features include hypogonadism, deafness, renal anomalies, and mild skeletal defects. [From OMIM]