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Triple X syndrome

Medically reviewed on Aug 16, 2017


Triple X syndrome, also called trisomy X, is a genetic disorder that affects about 1 in 1,000 females. Females normally have two X chromosomes in all cells — one X chromosome from each parent. In triple X syndrome, a female has three X chromosomes.

Many girls and women with triple X syndrome have no symptoms or only mild symptoms. In other cases, symptoms may be more pronounced — possibly including developmental delays and learning disabilities.

Treatment for triple X syndrome depends on which symptoms, if any, are present and their severity. Normal sexual development and the ability to have children are typical for most females who have triple X syndrome.


Signs and symptoms can vary greatly among girls and women with triple X syndrome. Some may experience no noticeable effect. Others may have mild symptoms. Occasionally significant symptoms may occur. If signs and symptoms do appear, they may include varying degrees of severity or any combination of these:

  • Taller than average height with especially long legs — the most typical physical feature
  • Delayed development of speech and language skills, as well as motor skills, such as sitting up and walking
  • Learning disabilities, such as difficulty with reading (dyslexia), understanding or math
  • Problems with fine and gross motor skills, memory, judgment and information processing (developmental dyspraxia)
  • Weak muscle tone (hypotonia)
  • Abnormally curved pinky fingers
  • Behavior and emotional problems
  • Vertical folds of skin that cover the inner corners of the eyes (epicanthal folds) or widely spaced eyes (hypertelorism)

Occasionally, triple X syndrome may be associated with these signs and symptoms:

  • Premature ovarian failure or ovary abnormalities
  • Infertility or menstrual irregularities
  • Early or late puberty
  • Constipation
  • Abdominal pains
  • Seizures
  • Kidney abnormalities
  • Frequent urinary tract infections
  • Flat feet
  • Abnormally shaped breastbone
  • Heart abnormalities

Generally, girls and women with triple X syndrome have intelligence in the normal range, but possibly slightly lower when compared with siblings.

When to see a doctor

If you're concerned about your daughter's development, make an appointment to talk with your family doctor or pediatrician. Your doctor can help determine the cause and suggest appropriate action.


Although triple X syndrome is genetic, it's usually not inherited — it's due to a random genetic error.

Normally, people have 46 chromosomes in each cell, organized into 23 pairs, which includes two sex chromosomes. One set of chromosomes is from the mother and the other set is from the father. These chromosomes contain genes, which carry instructions that determine everything from height to eye color.

The pair of sex chromosomes — either XX or XY — determines a child's sex. A mother can give the child only an X chromosome, but a father can pass on an X or a Y chromosome:

  • If the child receives an X chromosome from the father, the XX pair makes the child genetically a female.
  • If the child receives a Y chromosome from the father, the XY pair means the child is genetically a male.

Females with triple X syndrome have a third X chromosome from a random error in cell division. This error can happen before conception or early in the embryo's development, resulting in one of these forms of triple X syndrome:

  • Nondisjunction. In most cases, either the mother's egg cell or the father's sperm cell divides incorrectly, resulting in an extra X chromosome in the child. This random error is called nondisjunction, and all the cells in the child's body will have the extra X chromosome.
  • Mosaic. Occasionally, the extra chromosome results from an incorrect cell division caused by a random event early in the embryo's development. If this is the case, the child has a mosaic form of triple X syndrome, and only some cells have the extra X chromosome. So females with the mosaic form may have less obvious symptoms.

Triple X syndrome is also called 47,XXX syndrome because the extra X chromosome results in 47 chromosomes in each cell instead of the usual 46.


Although some females may have no or mild symptoms associated with triple X syndrome, developmental delays or learning disabilities often occur and may lead to a variety of other issues, including:

  • Work, school, social and relationship problems
  • Anxiety and other emotional problems, such as attention-deficit/hyperactivity disorder (ADHD) and autism symptoms
  • Behavior problems
  • Poor self-esteem
  • Need for additional assistance with learning, activities of daily living, school or work


Because many girls with triple X syndrome are healthy and have a normal appearance, they may remain undiagnosed all their lives, or the diagnosis may be discovered while checking other issues. Triple X syndrome can be confirmed by genetic testing — chromosome analysis using a blood sample.

Before genetic testing, it's important to receive genetic counseling to get comprehensive information about triple X syndrome.


The chromosome error that causes triple X syndrome can't be repaired, so the syndrome itself has no cure. Treatment is based on symptoms and needs. Options that may be helpful include:

  • Periodic screenings. Your daughter's doctor may recommend periodic screenings throughout childhood. If any developmental delays, learning disabilities or health problems occur, she can then receive prompt treatment.
  • Early intervention services. These services may include speech, occupational, physical or developmental therapy, starting in the early months of life or as soon as needs are identified.
  • Educational assistance. If your daughter has a learning disability, she can receive educational help to learn techniques and strategies to be successful in school and daily life.
  • Supportive environment and counseling. Girls with triple X syndrome may be more prone to anxiety, as well as behavior and emotional problems. So make sure your daughter has a supportive environment. And psychological counseling may help teach you and your family how to demonstrate love and encouragement, and discourage behaviors that might negatively impact learning and social functioning.
  • Assistance and support in daily functioning. If your daughter has developmental delays, this assistance and support may include help with activities of daily living, social opportunities and employment.

Coping and support

It's quite possible for your daughter to lead a full and happy life. However, sometimes help and support is needed. Both you and your daughter may benefit from these strategies:

  • Connect with others. Support groups provide help and support for people with X and Y chromosome disorders and their families. They offer information and advice on coping, as well as ways to meet and talk with others in similar situations. Ask your daughter's doctor or therapist if there is a local support group for similar types of disorders. You can also contact AXYS — association for X and Y chromosome variations.
  • Look for disability support resources. Coping with a learning disability is challenging. Get information on available services and sources of support. One example is the National Center for Learning Disabilities. Ask your daughter's school or therapist for information on additional resources.
  • Find ways to relieve stress. It's natural to feel overwhelmed at times. Talk about your concerns with a trusted friend or family member to help relieve your stress. Take some time for yourself doing something you like to do. Seek the help of outside caregivers who can give you a break from time to time.

Preparing for an appointment

Here's some information to help you get ready for your appointment, and what you might expect from your doctor. Preparing ahead of time can help you make the most of your time with the doctor. You may want to bring a family member or friend to the appointment for support and to help you remember information.

What you can do

Before your appointment, make a list of:

  • Any symptoms you've noticed in your daughter, including any that may seem unrelated to the reason for the appointment
  • Your daughter's developmental milestones and when she met them, such as learning to say her first word or learning to walk
  • Key personal information about your pregnancy, including any significant illnesses you may have experienced or any medications that you may have used
  • Any problems your daughter may be having with learning, emotions or behavior
  • Questions to ask your child's doctor

Some basic questions to ask the doctor include:

  • What's the most likely cause of my daughter's symptoms?
  • What kinds of tests does she need? Do these tests require any special preparation?
  • How might this condition affect her?
  • What treatments are available, and which do you recommend?
  • My daughter has other health conditions. How can we best manage these conditions together?
  • What services are available if my daughter has developmental delays or learning disabilities?
  • Are there any brochures or other printed materials that I can have? What websites do you recommend?

Don't hesitate to ask any other questions during your appointment.

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Be ready to answer them to reserve time to go over points you want to focus on. Your doctor may ask:

  • When did you first notice your daughter's symptoms?
  • Does anything seem to improve the symptoms?
  • What, if anything, appears to worsen the symptoms?
  • Did your daughter achieve developmental milestones on time, such as learning to talk or walk?
  • Has your daughter had any problems in school or other settings?

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