Trisomy X

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Trisomy X
Synonyms	Triple X syndrome, 47,XXX
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Specialty	Medical genetics
Symptoms	Tall stature, learning disabilities, developmental delay, hypotonia, epicanthic folds
Complications	N/A
Onset	Prenatal
Duration	Lifelong
Types
Causes	Nondisjunction during meiosis
Risks	Advanced maternal age
Diagnosis	Karyotype analysis
Differential diagnosis	Turner syndrome, Klinefelter syndrome, Down syndrome
Prevention	None
Treatment	Supportive care, speech therapy, occupational therapy
Medication
Prognosis	Generally good with support
Frequency	1 in 1,000 female births
Deaths

Age at diagnosis for Klinefelter syndrome, Trisomy X, and XYY syndrome

Trisomy X, also known as 47,XXX, is a chromosomal disorder that affects females. It is characterized by the presence of an extra X chromosome, resulting in a total of three X chromosomes instead of the usual two. This condition occurs in approximately 1 in 1,000 female births.

Genetics

Trisomy X is caused by nondisjunction during meiosis, which leads to an extra X chromosome in each cell. The karyotype for Trisomy X is 47,XXX. In some cases, mosaicism can occur, where some cells have the typical 46,XX karyotype and others have 47,XXX.

Karyotype showing mosaicism with 45,X0 and 47,XXX

Clinical Features

Many females with Trisomy X are asymptomatic and may never be diagnosed. However, some may exhibit mild symptoms such as tall stature, learning disabilities, and delayed speech and language development. Behavioral and emotional difficulties can also occur.

Estimated Full-Scale IQ distribution for females with 47,XXX compared to controls

Diagnosis

Trisomy X is often diagnosed through a karyotype analysis, which can be performed prenatally or postnatally. Prenatal diagnosis is possible through procedures such as amniocentesis or chorionic villus sampling.

Epidemiology

The prevalence of Trisomy X is estimated to be around 1 in 1,000 female births. However, due to the often mild or asymptomatic nature of the condition, many cases remain undiagnosed.

Expected and observed prevalence of sex chromosome aneuploidies in Denmark, including Trisomy X

Management

Management of Trisomy X is typically supportive and symptomatic. Educational support and speech therapy may be beneficial for those with learning disabilities or speech delays. Regular monitoring and follow-up with healthcare providers are recommended.

Prognosis

The prognosis for individuals with Trisomy X is generally good, with most leading normal lives. Lifespan is not significantly affected, and many women with Trisomy X have normal fertility.

See Also

• Klinefelter syndrome
• Turner syndrome
• Chromosomal disorder

References

• Tartaglia, N. R., Howell, S., Sutherland, A., Wilson, R., & Wilson, L. (2010). A review of trisomy X (47,XXX). Orphanet Journal of Rare Diseases, 5(1), 8.
• Leggett, V., Jacobs, P., Nation, K., Scerif, G., & Bishop, D. V. M. (2010). Neurocognitive outcomes of individuals with a sex chromosome trisomy: XXX, XYY, or XXY: A systematic review. Developmental Medicine & Child Neurology, 52(2), 119-129.