About Trisomy X

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Typically, a female has 2 X chromosomes. 1 in 1,000 females has an extra X. This is called Trisomy X. It is also written as 47,XXX.

As you can see in the adjoining photo collage of girls and young women with 47,XXX, the condition is not characterized by any prominent physical features. Children and adults with Trisomy X do not look different than their peers, though they may be somewhat taller. Some have a curved little finger, epicanthal eyelid fold (skin curving slightly down toward the inner eye), and flat feet. Some have very little in the way of symptoms, others have significant developmental, medical, and psychological issues.


47,XXX may produce the following additional symptoms, although most affected individuals will have only some of them:

  • Low muscle tone (can affect motor development and coordination)
  • Subtle developmental delays / delayed developmental milestones
  • Speech delay/expressive language disorder
  • Learning disabilities (such as dyslexia and difficulties with written expression)
  • Chronic stomach pain and constipation
  • Attention deficits (such as ADD or ADHD)
  • Depression, Anxiety, or other mood disorder
  • Behavioral differences including social skill impairment, immaturity, low self-esteem
  • Genitourinary or kidney malformations
  • Seizures
  • Tremors
  • Puberty and fertility are typically considered normal in 47, XXX; though there is increased risk of Premature Ovarian insufficiency (menstrual periods stop before age 40)

Because symptoms are subtle and vary widely from one person to the next, only 10 percent of those with Trisomy X are diagnosed during their lifetimes. More are being identified prenatally due to maternal testing (amniocentesis, CVS, or non-invasive cell free DNA blood test).

Adults may learn they have an extra X chromosome during infertility testing or during non-invasive prenatal testing when the mother’s extra X may be detected during cell-free DNA blood work.

The Importance of Testing

One of the goals of AXYS is to raise awareness of the developmental, medical and psychosocial issues that may accompany 47,XXX. Children with symptoms such as speech delay, learning disability, developmental delays or genitourinary malformations should be followed up with genetic testing to determine if the cause is an X and Y variation. 

Please visit our Prenatal Testing Page for more information regarding genetic testing: https://genetic.org/im-pregnant-genetic-testing-questions/prenatal-testing/


Frequently Asked Questions about 47,XXX

Downloadable Brochure- About 47,XXX (Trisomy X) Versión en español
Trifold brochure printing instructions: Be sure you are printing in two-sided (duplex) mode, and to select the “Flip on Short Edge” or “Short-Edge Binding” option, if available in the Print dialog box or any associated dialog boxes.

Living with Klinefelter Syndrome (47,XXY) Trisomy X (47, XXX) and 47, XYY: A Guide for Families and Individuals Affected by Extra X and Y Chromosome Variations

Thanks to the generosity of the book’s author, Virginia Isaacs Cover, MSW, AXYS is pleased to make this book available to the X and Y variation community, in its entirety, at no cost. Please feel free to download and/or print it for your personal use. Those wishing to purchase a soft-bound copy can do so at Amazon or Kindle. All proceeds from the sale of this book benefit the GALAXY registry of X and Y variations.

Spanish: “A Guide for Families and Individuals Affected by X and Y Chromosome Variations”

Trisomy X article by Nicole Tartaglia, et al | Spanish language version

Expanding the Phenotype of Triple X Syndrome by Nicole Tartaglia, et al

Talking to your daughter: “My Guide to Trisomy X

“Elizabeth and her Extra X”

Self Management Traffic Light Resource
This resource was created by an adult with Trisomy X. We’re grateful they shared it with us. We hope you find it helpful.

Facebook Support Groups

Trisomy X/Triple X/XXX Global Support Group

Trisomy X- A Group Just For Us

Other Trisomy X Websites

Contactgroep Triple-X Syndroom (The Netherlands)


Visit our CafePress store to support AXYS and raise awareness of Trisomy X.