Sex Chromosome Aneuploidies (SCA)

Most people have either two X chromosomes or one X and one Y chromosome in their cells. People with a sex chromosome aneuploidy (SCA) have a different number of X and/or Y chromosomes. The Harmony test looks for SCAs such as:

• Monosomy X (a cause of Turner syndrome)
• XXY (a cause of Klinefelter syndrome)
• XXX
• XYY
• XXYY

People with SCAs can have birth defects, infertility and learning differences. Some people with an SCA have such subtle features that the condition isn’t identified until after childhood.

Monosomy X (a cause of Turner syndrome)

Monosomy X is a condition in which a female has one X chromosome and no second sex chromosome. It occurs in about 1/2500 births¹ and is not typically inherited. Features are variable and can include endocrine (hormone) issues, heart defects and infertility.¹

For more detailed information about Monosomy X, including pregnancy management, health care guidelines, advocacy and support for families:

• https://rarediseases.org/rare-diseases/turner-syndrome
• https://turnersyndromefoundation.org
• https://www.turnersyndrome.org

XXY (a cause of Klinefelter syndrome)

XXY is a condition in which a male has two X chromosomes and one Y chromosome. It occurs in 1 in 500 to 1 in 1000 births² and is typically not inherited. Features are variable and often subtle, and largely involve the endocrine (hormone) system.²

For more detailed information about XXY, including pregnancy management, health care guidelines, advocacy and support for families:

• https://rarediseases.org/rare-diseases/klinefelter-syndrome
• https://genetic.org/variations/about-47xxy