Fragile X syndrome.
Fragile X syndrome is the most common familial form of mental retardation. This X-linked disorder affects one in every 1000 males and one in every 2000 females. The female carrier rate in the general population is estimated to be 1/600. A fragile site at the distal long arm of the X chromosome (Xq 27.3) is the hallmark cytogenetic feature of the syndrome. Clinical features include physical as well as cognitive and neuropsychological deficits. Although fragile X syndrome follows an X-linked pattern of inheritance (which explains the predominance of affected males), females can also be affected. Many inconsistencies exist between the genetic inheritance pattern of fragile X and traditional Mendelian inheritance tenets of most X-linked diseases. Due to recent molecular advances, our understanding of the perplexing genetic issues surrounding fragile X syndrome has grown and diagnostic techniques have become both reliable and readily available.
Donnenfeld
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Department of Obstetrics and Gynecology, Pennsylvania Hospital, University of Pennsylvania School of Medicine, Philadelphia, USA. donnenfl@jeflin.tju.edu
D002648:Child; D005260:Female; D005600:Fragile X Syndrome / Q000175:diagnosis* / Q000235:genetics; D006580:Genetic Carrier Screening; D005817:Genetic Counseling; D005820:Genetic Testing; D006801:Humans; D007621:Karyotyping; D008297:Male; D011247:Pregnancy