Reviewed January 2006
What is triple X syndrome?
Triple X syndrome, also called trisomy X or 47,XXX, is characterized by the presence of one extra X chromosome in each of a female's cells. Most often, this chromosomal change causes no unusual physical features or medical problems. Females with triple X syndrome are sometimes taller than average and have an increased risk of learning disabilities and delayed speech and language skills. Developmental delays and behavioral problems are also possible, but these characteristics vary widely among affected girls and women. Most females with triple X syndrome have normal sexual development and are able to conceive children.
How common is triple X syndrome?
This condition occurs in about 1 in 1,000 newborn girls. Five to 10 girls with triple X syndrome are born in the United States each day.
What are the genetic changes related to triple X syndrome?
Triple X syndrome is related to the X chromosome.
People normally have 46 chromosomes in each cell. Two of the 46 chromosomes are sex chromosomes, called X and Y. Females have two X chromosomes (46,XX), and males have one X chromosome and one Y chromosome (46,XY).
Triple X syndrome results from an extra copy of the X chromosome in each of a female's cells. As a result of the extra X chromosome, each cell has a total of 47 chromosomes (47,XXX) instead of 46. It remains uncertain why an extra copy of the X chromosome is associated with tall stature and learning problems in some girls and women.
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 mosaics.
Can triple X syndrome be inherited?
Trisomy X usually is not inherited, but occurs as a random event during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of the X chromosome as a result of nondisjunction. If one of these atypical reproductive cells contributes to the genetic makeup of a female child, the child will have an extra X chromosome in each of the body's cells.
In some cases, trisomy X results from nondisjunction during cell division in early embryonic development. These cases are usually 46,XX/47,XXX mosaics.
Where can I find information about treatment for triple X syndrome?
You may find information on treatment or management of triple X syndrome or some of its symptoms in the links below, particularly the links for
Educational resources and Patient support.
Where can I find additional information about triple X syndrome?
You may find the following resources about triple X syndrome helpful. These materials are written for the general public.
- MedlinePlus - Health information
- Health Topic: Learning Disorders (http://www.nlm.nih.gov/medlineplus/learningdisorders.html)
- Health Topic: Speech and Communication Disorders (http://www.nlm.nih.gov/medlineplus/speechandcommunicationdisorders.html)
- Educational resources - Information pages
- Ask the Geneticist: Overview of triple X syndrome (http://www.genetics.emory.edu/ask/question.php?question_id=531)
- Ask the Geneticist: Risk of having a child with triple X syndrome (http://www.genetics.emory.edu/ask/question.php?question_id=2771)
- Ask the Geneticist: Triple X syndrome and 46,XX/47,XXX mosaicism (http://www.genetics.emory.edu/ask/question.php?question_id=1803)
- Madisons Foundation (http://www.madisonsfoundation.org/index.php/component/option,com_mpower/diseaseID,280/)
- March of Dimes: Chromosomal Abnormalities (http://www.marchofdimes.com/professionals/14332_1209.asp)
- Merck Manual Home Edition for Patients and Caregivers (http://www.merck.com/mmhe/sec23/ch266/ch266f.html)
- National Library for Health, National Health Service (UK) (http://www.library.nhs.uk/geneticconditions/viewresource.aspx?resID=93920)
- New York Online Access to Health (NOAH) (http://www.noah-health.org/en/genetic/conditions/xxx.html)
- Orphanet (http://www.orpha.net//consor/cgi-bin/OC_Exp.php?Lng=EN&Expert=3375)
- The Pacific Northwest Regional Genetics Group (http://mchneighborhood.ichp.edu/pacnorgg/media/Sex_Chrom/xxx_eng.pdf)
- The Turner Center, Denmark: Triple-X Females: An Orientation (http://www.aaa.dk/TURNER/ENGELSK/TRIPLEX.HTM)
- University of Michigan Health System (http://www.med.umich.edu/1libr/yourchild/xxxsyn.htm)
- Patient support - For patients and families
- Klinefelter Syndrome and Associates (http://www.genetic.org/knowledge/support/action/200/)
- National Organization for Rare Disorders (http://www.rarediseases.org/search/rdbdetail_abstract.html?disname=Triplo+X+Syndrome)
- Resource list from the University of Kansas Medical Center (http://www.kumc.edu/gec/support/chromoso.html#xxx)
- Unique: The Rare Chromosome Disorder Support Group (UK) (http://www.rarechromo.org/)
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
- PubMed - Recent literature (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=PubMed&term=((triple+x[TIAB])+OR+(47+AND+XXX[TI])+OR+(trisomy+x[TIAB])+OR+(triplo+x[TIAB])+OR+(xxx+syndrome[TIAB]))+AND+english[la]+AND+human[mh]&orig_db=PubMed&filters=ON&pmfilter_EDatLimit=3600+Days)
What other names do people use for triple X syndrome?
- Triplo X syndrome
- Trisomy X
- 47,XXX
- XXX syndrome
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
What if I still have specific questions about triple X syndrome?
- See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.
- Ask the Genetic and Rare Diseases Information Center (http://rarediseases.info.nih.gov/GARD/).
- Submit your question to Ask the Geneticist (http://www.askthegen.org/).
What glossary definitions help with understanding triple X syndrome?
atypical ;
cell ;
cell division ;
chromosome ;
developmental delay ;
egg ;
embryonic ;
learning disability ;
mosaic ;
nondisjunction ;
reproductive cells ;
sex chromosomes ;
sperm ;
stature ;
syndrome ;
trisomy
You may find definitions for these and many other terms in the Genetics Home Reference
Glossary (http://ghr.nlm.nih.gov/glossary).
References
- Haverty CE, Lin AE, Simpson E, Spence MA, Martin RA. 47,XXX associated with malformations. Am J Med Genet. 2004 Feb 15;125A(1):108-11; author reply 112. Review. No abstract available. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=14755479)
- Linden MG, Bender BG, Robinson A. Genetic counseling for sex chromosome abnormalities. Am J Med Genet. 2002 Jun 1;110(1):3-10. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=12116264)
- Linden MG, Bender BG. Fifty-one prenatally diagnosed children and adolescents with sex chromosome abnormalities. Am J Med Genet. 2002 Jun 1;110(1):11-8. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=12116265)
- Nussbaum, Robert L; McInnes, Roderick R; Willard, Huntington F; Thompson, Margaret W((Margaret Wilson),); Thompson & Thompson genetics in medicine.; 6th ed., rev. reprint / Robert L. Nussbaum, Roderi; Philadelphia : Saunders, c2004.
The resources on this site should not be used as a substitute for
professional medical care or advice. Users seeking information about
a personal genetic disease, syndrome, or condition should consult with a qualified
healthcare professional.
See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.
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