Syndrome triple X
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2008-06-20T16:24:07Z
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{{ébauche|médecine}}
Le '''syndrome triple X''' est une anomalie [[chromosome|chromosomale]] [[aneuploïdie|aneuploïdique]] caractérisée par la présence d'un [[chromosome X]] supplémentaire dans chaque [[cellule (biologie)|cellule]] d'une [[femme]]. Le syndrome est également appelé '''syndrome XXX''', '''trisomie X''', '''triplo-X''', '''47xxx''' ou '''aneuploïdie 47,XXX'''. Cette anomalie chromosomique se déclenche lors de la méiose.
La trisomie-X apparaît lors de la division des [[gamète]]s des parents. Des femmes atteintes de trisomie-X sont typiquement grandes avec des seuils de sensibilité légèrement plus élevés, et ne présentent pas de risques accrus sur le plan médical.
== Symptômes ==
<!--Most often, triple X syndrome causes no unusual physical features or [[medicine|medical]] problems. Females with the syndrome are usually [[human height|taller]] than average, may have [[menstrual cycle|menstrual]] irregularities, and, although rarely exhibiting severe learning difficulties (US: mentally retarded), sometimes have an increased risk of [[learning disability|learning disabilities]] and delayed speech and language skills. Researchers are not yet certain why an extra copy of the X chromosome is associated with tall stature and learning issues in some girls and women. These characteristics vary widely among affected individuals, however. Additionally, most females with triple X syndrome have normal [[human sexuality|sexual development]] and are able to [[fertilisation|conceive]] [[child]]ren.-->
== Causes ==
<!--Triple X syndrome is not inherited, but usually occurs as a random event during the formation of [[reproduction|reproductive cell]]s ([[ovum]] and [[sperm]]). An error in cell division called [[nondisjunction]] can result in reproductive cells with an abnormal number of chromosomes. For example, an [[oocyte]] or sperm cell may gain an extra copy of the X chromosome as a result of the nondisjunction. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra X chromosome in each of his or her cells. In some cases, trisomy X occurs as an accident during cell division in early [[fetus|fetal]] development.
Some females with triple X syndrome have an extra X chromosome in only some of their cells. These cases are called 46,XX/47,XXX [[mosaic (genetics)|mosaic]]s.-->
Causée comme toute trisome suite à une mal-ségrégation chromosomique survenant lors de la [[gamétogenèse]] ou plus précisément l'[[ovogenèse]] (donc chez la femme uniquement) car seule la femme possède deux [[Chromosome X|chromosomes X]] dans le noyau de ses cellules. De même, comme toutes trisomies ou plus généralement toutes les [[aneuploïdie]]s, leurs occurrences augmentent avec l'âge de la mère.
== Incidence ==
<!--Triple X syndrome occurs in about 1 in 1,000 newborn girls. Five to ten girls with triple X syndrome are born in the [[United States]] each day.-->
== Liens externes ==
<!--* {{en}} [http://ghr.nlm.nih.gov/condition=triplexsyndrome Triple X syndrome] at the NLM Genetics Home Reference site
* {{en}} [http://www.aaa.dk/turners/engelsk/triplex.htm]
*Community & Support
** {{en}} [http://www.triplo-x.org/]
** {{en}} [http://www.groups.yahoo.com/group/ktxgroup/] -->
{{Chromosome humain}}
{{Portail médecine}}
[[Catégorie:Maladie génétique|Triple X]]
[[Catégorie:Maladie chromosomique|Triple X]]
[[cs:XXX syndrom]]
[[de:Triplo-X-Syndrom]]
[[en:Triple X syndrome]]
[[es:Síndrome del triple X]]
[[hu:Tripla X-szindróma]]
[[it:Sindrome della tripla X]]
[[nl:Triple X-syndroom]]
[[pl:Trisomia chromosomu X]]
[[pt:Trissomia X]]
[[sv:XXX syndrom]]
[[zh:X-三體]]