X and Y Chromosome Variations

If you have just found out through prenatal testing that your baby has or may have a variation of the number of X or Y chromosomes and are looking for more information, the Genetic Support Foundation is a good starting point.

There are many other important resources out there, including your doctor and genetic counselor. We have also compiled a list of resources that can provide you with additional information and support. After reviewing the information below, if you have a question that you are having difficulty finding an answer for, please feel free to contact us.


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Overview of Important Information about X and Y Chromosome Variations

X and Y chromosome variations are conditions that result when a baby has an atypical number of sex chromosomes, also known as X&Y chromosomes in some or all their cells.  Typically, girls have two X chromosomes while boys have one X and one Y chromosome.  Many variations from this number can occur and are also sometimes referred to as “sex chromosome anomaly,” “sex chromosome abnormality” and “sex chromosome aneuploidy.”

The most common variations involve a trisomy, which means three sex chromosomes instead of the typical two. Girls who are born with an extra X chromosome are referred to as having Triple X or Trisomy X. Boys who are born with an extra X chromosome have 47,XXY, also known as Klinefelter syndrome. And boys who are born with an extra Y chromosome have 47,XYY, occasionally referred to as Jacob’s syndrome.

In addition, there are a number of other X and/or Y conditions including 48 or 49 chromosomes. These include 48,XXXX, 48XXXY, 48XXYY and 48XYYY; and although increasingly rare, also 49XXXXX, 49XXXXY, 49XXXYY, 49XXYYY and 49XYYY. Some individuals may have two cell lines, which is called mosaicism, such as 46,XY/47,XXY.



What Causes X and Y Chromosome Variations?

It is important to remember that the signs and symptoms of X and Y chromosome variations can vary quite a bit from person to person.  During pregnancy, the conditions may be diagnosed through genetic testing such as a chorionic villus sampling (CVS) or amniocentesis or may be suspected through a blood test such as cell free DNA analysis. Keep in mind that cell free DNA analysis cannot tell for certain if a baby has a variation in their number of X and Y chromosomes.



If I have a baby with an X and Y chromosome variation, what is the chance I will have another baby with this condition?

In most cases, the chance that a woman will have another baby with an X and Y chromosome variation is thought to be less than 1% as the majority of cases of X and Y chromosome variation are not inherited.



Treatment for X and Y Chromosome Variations

There is no “cure” for X and Y chromosome variations as the genetic changes that cause the conditions are typically present in some or all of the cells in the person’s body.

Individuals who have X and Y chromosome variations will need to undergo regular check-ups to maintain their health.  Early intervention and support in school can help with learning disabilities.   While hormone supplementation can assist with differences in height and normal pubertal development.



How common are X and Y Chromosome Variations?

Variations in the number of X and Y chromosomes are estimated to occur in one of every 400 to 500 newborns.



Outlook

Most individuals with X and Y chromosome variations will have differences in final adult height and have infertility.  Some will experience difficulties in learning, however, many have success in school, including higher education.  Men and women with X and Y chromosome disorders work in a variety of career settings.  Some may have children on their own or with the help of assisted reproductive technologies.  While others may choose to adopt.  Individuals with X and Y chromosome variations often benefit from careful monitoring of their health throughout their life.  However, most can expect to live full and productive lives.









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