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Turner syndrome
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My stepdaughter has Turner syndrome. I was wondering if her mother or father carries the gene that causes this disease? Would a blood test from her father indicate if it came from his side of the family?

What is Turner syndrome?
What causes Turner syndrome?
Is Turner syndrome inherited?
How can I find a genetics professional in my community?

What is Turner syndrome? (Back to Top)
Turner syndrome is a chromosomal disorder that occurs in females and is caused by the complete or partial absence of an X chromosome. Turner syndrome may cause shortened stature, infertility, extra skin on the neck (webbed neck), puffiness or swelling (lymphedema) of the hands and feet, skeletal abnormalities, heart defects, and kidney problems.^[1] Symptoms differ from person to person. Many of the symptoms of Turner syndrome can be improved or corrected with treatment.
Last Reviewed: 4/8/2008
What causes Turner syndrome? (Back to Top)
Turner syndrome is a disorder caused by the loss of genetic material from one of the sex chromosomes.

Humans normally have a total of 46 chromosomes (which are tiny, DNA-containing elements) that are present in every cell of the body. DNA encodes genes, which specify all the proteins that make up the body and control its functions.

In humans, there are 23 matched pairs of chromosomes in every cell. Each cell contains 22 pairs of chromosomes called autosomes that are the same in males and females. The remaining pair of chromosomes, the X- and Y-chromosomes, are not shaped similarly, and thus are not matched in the same way as the autosomes.

The X- and Y-chromosomes are called sex chromosomes. They are responsible for the difference in development between males and females. A Y-chromosome contains genes responsible for testis development; and the presence of a X-chromosome paired with a Y-chromosome will determine male development. On the other hand, two X-chromosomes are required for normal ovarian development in females.^[3]

In Turner syndrome, the individual does not have the usual pair of two complete X chromosomes. The most common scenario is that she has only one X chromosome in her cells.^[2] An error in cell division called nondisjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may lose a sex chromosome as a result of nondisjunction. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have a single X chromosome in each cell and will be missing the other sex chromosome.^[1]

Some girls with Turner syndrome do have two X chromosomes, but one of the X chromosomes is incomplete.^[2] For example, one X-chromosome may be fragmented, have portions deleted or other structural problems such as ring formation preventing the normal expression of X-chromosome genes. The clinical consequences of having one normal and one structurally defective X-chromosome vary widely. A small deletion may result in a single feature such as ovarian failure or short stature and no other effects. Larger deletions or deletions affecting critical areas regulating the whole chromosome may result in a full spectrum of Turner syndrome problems. The diagnosis of abnormal X-chromosomes may require specialized, molecular cytogenetic studies to identify small deletions or inversions of X-chromosome material.^[3]

In another scenario, the child has some cells in her body with two X chromosomes, but other cells have only one. This is called mosaicism.^[2] X-chromosome mosaicism is also not inherited. It occurs as a random error during cell division in early fetal development. As a result, some of an affected person's cells have the usual two sex chromosomes, and other cells have only one copy of the X chromosome.^[1]
Last Reviewed: 10/24/2008
Is Turner syndrome inherited? (Back to Top)
Turner syndrome is not usually inherited in families. Although the exact cause of Turner syndrome is not known, it appears to occur as a result of a random error during the formation of either the eggs or sperm.^[1]^[2]^[3]

The one exception to this observation are families with a X-chromosome deletion which is stable enough to be passed down through the generations and which also allows fertility.^[3] A karyotype can identify the type of Turner syndrome affecting an individual. This type of genetic test can be performed with the help of a genetics professional. This type of medical professional can also address any additional questions or concerns you may have about the genetics and inheritance of Turner syndrome.
Last Reviewed: 4/8/2008
How can I find a genetics professional in my community?
(Back to Top)
We suggest that you consult with a genetics professional because this condition can be inherited. To find a genetics professional near you we recommend you speak with your health care provider. Click here to learn more about genetic consultations.

The following online resources can also help you find a genetics professional in your community:

* GeneTests - A searchable directory of US and international genetics and prenatal diagnosis clinics. To locate genetics clinics in the United States, go to the following link and click on "Clinic Directory" to find a genetic service close to you. To locate genetics clinics outside of the United States, go the following link, click on "Clinic Directory", and click on "International Clinic Directory Search".
http://www.geneclinics.org/

* ResourceLink - A database of genetic counseling services, searchable by location, name, institution, type of practice, or specialty. Hosted by the National Society of Genetic Counselors.
http://www.nsgc.org/resourcelink.cfm

* Genetic Centers, Clinics, and Departments - A comprehensive resource list for genetic counseling, including links to genetic centers and clinics, associations, and university genetics departments. Hosted by the University of Kansas Medical Center.
http://www.kumc.edu/gec/prof/genecntr.html

* The American Society of Human Genetics (ASHG) is a professional organization of research and clinical geneticists. The ASHG maintains a database of these geneticists, some of which live outside of the United States. If you are interested in obtaining a list of the geneticists in your area, some of which may only be researchers and may not offer medical care, please visit the following hyperlink, and search using your city, state, and/or country.
http://genetics.faseb.org/cgi-bin/ASHG-Search
Last Reviewed: 8/25/2008

References (Back)

Turner syndrome. Genetic Home Reference. September 2005 Available at: http://ghr.nlm.nih.gov/condition=turnersyndrome. Accessed April 7, 2008.
Learning About Turner Syndrome. National Human Genome Research Institute (NHGRI). November 27, 2007 Available at: http://www.genome.gov/19519119. Accessed April 7, 2008.
Genetic Features of Turner Syndrome. National Institute of Child Health and Human Development (NICHD) . September 27, 2004 Available at: http://turners.nichd.nih.gov/genetic.html. Accessed August 8, 2008.

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