Several other syndromes, characterised by the association of severe mental retardation with dysmorphic features, are caused by allelic mutations in the ATRX gene: Juberg-Marsidi [34], X-linked mental retardation with spastic paraplegia [6], Carpenter-Waziri [39], Holmes-Gang [5], Smith-Fineman-Myers [40] and Chudley-Lowry [31] syndromes. This evidence concerns the gene ATRX and Spastic paraplegia.