Turner Syndrome

DEFINITION

Turner syndrome, a condition that affects only girls and women, results when a sex chromosome (the X chromosome) is missing or partially missing. Turner syndrome can cause a variety of medical and developmental problems, including short height, failure to start puberty, infertility, heart defects, certain learning disabilities and social adjustment problems.

Turner syndrome may be diagnosed before birth (prenatal), during infancy or in early childhood. Occasionally the diagnosis is delayed until the teen or young adult years in those who have mild signs and symptoms of Turner syndrome.

Nearly all girls and women with Turner syndrome need ongoing medical care from a variety of specialists. Regular checkups and appropriate care can help most girls and women lead relatively healthy, independent lives.

CAUSES

Most people are born with two sex chromosomes. A boy inherits the X chromosome from his mother and the Y chromosome from his father. A girl inherits one X chromosome from each parent. If a girl has Turner syndrome, one copy of the X chromosome is missing or significantly changed.

The genetic alterations of Turner syndrome may be one of the following:

• Monosomy. The complete absence of an X chromosome generally occurs because of an error in the father’s sperm or in the mother’s egg. This results in every cell in the body having only one X chromosome.
• Mosaicism. In some cases, an error occurs in cell division during early stages of fetal development. This results in some cells in the body having two complete copies of the X chromosome. Other cells have only one copy of the X chromosome, or they have one complete and one altered copy.
• Y chromosome material. In a small percentage of Turner syndrome cases, some cells have one copy of the X chromosome and other cells have one copy of the X chromosome and some Y chromosome material. These individuals develop biologically as girls, but the presence of Y chromosome material increases the risk of developing a type of cancer called gonadoblastoma.

Effect of the chromosomal errors

The missing or altered X chromosome of Turner syndrome causes errors during fetal development and other developmental problems after birth — short stature, ovarian failure and learning disabilities.

SYMPTOMS

Signs and symptoms of Turner syndrome may vary significantly.

Before birth

Prenatal ultrasound of a baby with Turner syndrome may show:

• Large fluid collection on the back of the neck or other abnormal fluid collections
• Heart abnormalities
• Abnormal kidneys

At birth or during infancy

In some girls, a number of physical features and poor growth are apparent early. Signs of Turner syndrome at birth or during infancy may include:

• Wide or weblike neck
• Receding or small lower jaw
• High, narrow roof of the mouth (palate)
• Low-set ears
• Low hairline at the back of the head
• Broad chest with widely spaced nipples
• Short fingers and toes
• Fingernails and toenails that are narrow and turned upward
• Swelling of the hands and feet, especially at birth
• Slightly smaller than average height at birth
• Delayed growth

In older girls, teens and young women

For some girls, the presence of Turner syndrome may not be readily apparent. Signs and symptoms in older girls, teenagers and young women that may indicate Turner syndrome include:

• No growth spurts at expected times in childhood
• Short stature, with an adult height of about 8 inches (20 centimeters) less than might be expected for a female member of her family
• Learning disabilities, particularly with learning that involves spatial concepts or math, though intelligence is usually normal
• Difficulty in social situations, such as problems understanding other people’s emotions or reactions
• Failure to begin sexual changes expected during puberty — due to ovarian failure that may have occurred by birth or gradually during childhood, adolescence or young adulthood
• Sexual development that “stalls” during teenage years
• Early end to menstrual cycles not due to pregnancy

For most women with Turner syndrome, inability to conceive a child without fertility treatment

When to see a doctor

Sometimes it’s difficult to distinguish the signs and symptoms of Turner syndrome from other disorders. So it’s important to get a prompt, accurate diagnosis and appropriate care. See your doctor if you believe your daughter shows signs of Turner syndrome or if you have concerns about her physical, sexual or behavioral development.