X-chromosome linked diseases neurological disorders Rett syndrome Defect of the Methyl-CpG-binding protein 2(MeCP-2 protein), which mediates transcriptional repression through nteraction with histone deacetylase. Defects in mecp2 are the cause of rett syndrome a progressive neurologic developmental disorder and one of the most common causes of mental retardation in females. Patients appear to develop normally until 6 to 18 months of age, then gradually lose speech and purposeful hand movements and develop microcephaly, seizures, autism, ataxia, intermittent hyperventilation, and stereotypic hand movements It affects females almost exclusively, because the defect is lethal in boys Lesch-Nyhan syndrome Caused by deficiency of the enzyme hypoxanthine phosphoribosyl transferase(HRT)( purine recycling hyperuricaemia( purine metabolites), Characteristic neurological features including selfmutilation, choreoathetosis spasticity and mental retardation( last one unclear relationship with the enzyme defect Only males McLeod syndrome Lack of membrane transport protein XK. Characterized by late onset abnormalities in the neuromuscular and hematopoietic systems Only males Mohr-Tranebjaerq syndrome LosS-of-function mutations in the Deafness dystonia protein 1 gene. This protein belongs to a protein family which mediate the import and insertion of hydrophobic membrane proteins into the mitochondrial inner membrane. A syndrome of deafness, visual impairment leading to blindness, dystonia, multiple fractures, and mental retardation without other clinical manifestations Only malesRett syndrome Defect of the Methyl-CpG-binding protein 2 (MeCP-2 protein), which mediates transcriptional repression through interaction with histone deacetylase . Defects in mecp2 are the cause of rett syndrome a progressive neurologic developmental disorder and one of the most common causes of mental retardation in females. Patients appear to develop normally until 6 to 18 months of age, then gradually lose speech and purposeful hand movements and develop microcephaly, seizures, autism, ataxia, intermittent hyperventilation, and stereotypic hand movements. It affects females almost exclusively, because the defect is lethal in boys Mohr-Tranebjaerg syndrome Loss-of-function mutations in the Deafness dystonia protein 1 gene . This protein belongs to a protein family which mediate the import and insertion of hydrophobic membrane proteins into the mitochondrial inner membrane. A syndrome of deafness, visual impairment leading to blindness, dystonia, multiple fractures, and mental retardation without other clinical manifestations. Only males Lesch-Nyhan syndrome Caused by deficiency of the enzyme hypoxanthine phosphoribosyl transferase (HRT)( purine recycling ) Hyperuricaemia( purine metabolites),Characteristic neurological features including selfmutilation ,choreoathetosis, spasticity and mental retardation ( last one unclear relationship with the enzyme defect ) Only males McLeod syndrome Lack of membrane transport protein XK . Characterized by late onset abnormalities in the neuromuscular and hematopoietic systems. Only males X-chromosome linked diseases , neurological disorders