47,XYY affects about 1 in 1,000 males. Adding to its relative rarity, it is diagnosed in only about 10 percent of cases, often during prenatal testing.

Many with 47,XYY have no symptoms at all. Others can demonstrate significant developmental and behavioral issues.

47,XYY was sometimes referred to as “Jacob’s syndrome.”

XYY Symptoms

47,XYY may produce a wide array of symptoms, although most people with the extra Y chromosome it entails will exhibit only some, but not all, of the following:

  • Tall stature
  • Low muscle tone
  • Speech delay/expressive language disorder
  • Subtle developmental delays
  • Autism
  • Learning disability
  • Attention deficits
  • Depression/anxiety

The Case for Testing

When children show a history of symptoms such as speech delay, learning disability, or autism, parents should strongly consider genetic testing to determine if the cause is a sex chromosome aneuploidy (SCA). Testing for 47,XYY involves a specialized blood test, either a “karyotyping” or a “microarray.” Health care professionals are often unfamiliar with the developmental and cognitive deficits associated with X & Y variations.

Frequently Asked Questions about 47,XYY

Downloadable Brochure- About 47,XYY
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 Isaac’s 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 AXYS.)

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

What is XYY? Meet Steve and find out.

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