A survey of the mentally retarded children with an IQ between 30 and 55 born in a 10-year period (1955-64) and now of school age was carried out in New South Wales. The number of propositi who had a similarly affected sib of the same sex was ascertained; 58 boys had a similarly affected brother(s) and 22 girls had a similarly affected sister(s). It is suggested that the excess of affected broth...

x-chromosome inactivation (xci) is a process by which one of the copies of the x chromosome in mammalian female cells is inactivated. the xci causes a balanced x-linked gene quantity between male and females; moreover, it results mosaic females which have paternal active x in some cells and maternal active x in others. cellular mosaicism is a noteworthy phenomenon and lowers the risk of x-linke...

Non-syndromic mental retardation is one of the most serious neurodevelopmental disorders, which has a serious impact not only on the affected individuals and their families but also on the health care system and society. Previously research has been more focused on the X-linked mental retardation and only recently studies have shown that non-syndromic autosomal recessive mental retardation is e...

We evaluated a kindred with X-linked mental retardation and epilepsy. Seven affected males with mild to moderate mental retardation developed seizures (primarily generalized, tonic-clonic, and atonic) that began on average at 6.8 months of age (range, 4 to 14 months). These patients did not have a history of infantile spasms. There were no dysmorphic features. Other than mental retardation, the...