Turner Syndrome

Monosomy X (45,X), or Turner syndrome, results when an individual inherits one X chromosome and no second sex chromosome. All individuals with Turner syndrome are female. This is because presence of the Y chromosome is required for male development; in its absence, all fertilized eggs default to becoming female.

Most often, 45,X results when an egg containing 23 chromosomes is fertilized by a sperm containing only 22 chromosomes, lacking a sex chromosome. Of conceptions with a 45,X karyotype, 99% end in miscarriage (Jorde et al., 2000). Approximately 1 in 2,500 to 1 in 5,000 females are born with Turner syndrome (Jorde et al., 2000).

Most people with Turner syndrome have normal intelligence and are active members of their communities. To the majority of the community, the diagnosis of Turner syndrome is likely not apparent. Individuals with Turner syndrome commonly have the following characteristics:

• Short stature
• Absence of ovaries and failure to proceed through puberty
• Characteristic facial features and a webbed neck
• Congenital heart defects

Features associated with Turner syndrome are caused by the absence of the "second dose" of genetic information contained on the short arm of the X chromosome. To learn more about Turner syndrome, visit eMedicine. The site has a complete system review and photos of children with Turner syndrome.