Trisomy X is a caused by the presence of an extra X chromosome in females (47,XXX instead of 46,XX). This is also the most common female chromosomal abnormality, occurring in approximately 1 in 1,000 female births.
Other abnormalities of chromosome number include: female tetrasomy X (quadruple X, or 48, XXXX) a rare chromosomal disorder and male Klinefelter syndrome, the presence of an additional X chromosome (47, XXY or XXY).
- Alternative names: Triplo X syndrome, Trisomy X, 47,XXX, XXX syndrome
Some Recent Findings
The most common prenatal diagnosis is by either amniocentesis or chorionic villi sampling.
|Feature||Estimated frequency based on current available data|
|Tall stature >75th percentile||80 - 89 %|
|Epicanthal folds||32 - 46 %|
|Clinodactyly||42 - 65 %|
|Hypotonia in infancy||55 - 71 %|
|Genitourinary malformations||5 - 16 %|
|Seizure disorder||11 - 15 %|
|Intention tremor||6 - 20 %|
|Congenital hip dysplasia||2 - 12 %|
|Constipation/Abdominal pains||12 - 45 %|
|Premature ovarian failure||unknown|
Table data from Tartaglia NR, etal., 2010
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Search Pubmed: Trisomy X
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Cite this page: Hill, M.A. (2019, August 21) Embryology Trisomy X. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Trisomy_X
- © Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G