Triple X syndrome


Triple X syndrome, also called trisomy X or 47,XXX, 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 don't experience symptoms or have only mild symptoms. In others, symptoms may be more apparent — possibly including developmental delays and learning disabilities. Seizures and kidney problems occur in a small number of girls and women with triple X syndrome.

Treatment for triple X syndrome depends on which symptoms, if any, are present and their severity.


Signs and symptoms can vary greatly among girls and women with triple X syndrome. Many experience no noticeable effects or have only mild symptoms.

Being taller than average height is the most typical physical feature. Most females with triple X syndrome experience normal sexual development and have the ability to become pregnant. Some girls and women with triple X syndrome have intelligence in the normal range, but possibly slightly lower when compared with siblings. Others may have intellectual disabilities and sometimes may have behavioral problems.

Occasionally, significant symptoms may occur, which vary among individuals. These signs and symptoms may show up as:

  • 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, understanding or math
  • Behavioral problems, such as attention-deficit/hyperactivity disorder (ADHD) or symptoms of autism spectrum disorder
  • Psychological problems, such as anxiety and depression
  • Problems with fine and gross motor skills, memory, judgment and information processing

Sometimes females with triple X syndrome have these signs and symptoms:

  • Vertical folds of skin that cover the inner corners of the eyes (epicanthal folds)
  • Widely spaced eyes
  • Curved pinky fingers
  • Flat feet
  • Breastbone with an inward bowed shape
  • Weak muscle tone (hypotonia)
  • Seizures
  • Problems with the kidneys
  • Ovaries that don't work properly at a young age (premature ovarian failure)

When to see a doctor

If you're concerned about any signs or symptoms, make an appointment to talk with your family health care provider or pediatrician, who 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, including 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 female.
  • If the child receives a Y chromosome from the father, the XY pair means the child is genetically 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. 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 mild or no symptoms associated with triple X syndrome, others experience developmental, psychological and behavioral problems that may lead to a variety of other issues, including:

  • Work, school, social and relationship problems
  • Poor self-esteem
  • Need for additional support or assistance with learning, activities of daily living, school or work


Because many girls and women with triple X syndrome are healthy and show no outward signs of the condition, they may remain undiagnosed all their lives, or the diagnosis may be discovered while checking other issues. Triple X syndrome may also be discovered during prenatal testing to identify other genetic disorders.

During pregnancy, a sample of the mother's blood can be tested to check the baby's DNA. If the test shows an increased risk of triple X syndrome, a sample of fluid or tissue from inside the womb can be collected. Genetic testing of the fluid or tissue will show if there's an extra, third, X chromosome.

If triple X syndrome is suspected after birth based on signs and symptoms, it can be confirmed by genetic testing. In addition to genetic testing, genetic counseling can help you gain 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. The health care provider may recommend periodic screenings throughout childhood and into adulthood. If any developmental delays, learning disabilities or health problems occur, prompt treatment can be provided.
  • 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 child has a learning disability, educational help to learn techniques and strategies to be successful in school and daily life can be provided.
  • Supportive environment and counseling. Girls and women with triple X syndrome may be more prone to anxiety, as well as behavioral and emotional problems. So make sure your child has a supportive environment. 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 child has problems that impact daily functioning, this assistance and support may include help with activities of daily living, social opportunities and employment.

Coping and support

It's quite possible for girls and women with triple X syndrome to lead full and happy lives. However, sometimes help and support are needed. Both you and your child 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 child's health care provider or therapist if there is a local support group for people with similar types of disorders. You can also contact AXYS — the 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 child'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 your appointment

Here's some information to help you get ready for your appointment, and what you might expect from your health care provider. 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 signs or symptoms you've noticed in your child, including any that may seem unrelated to the reason for the appointment
  • Your child's developmental milestones and when they were met, such as learning to say first words 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 child may be having with learning, emotions or behavior
  • Questions to ask your child's health care provider

Some basic questions to ask the health care provider include:

  • What's the most likely cause of my child's symptoms?
  • What kinds of tests does my child need? Do these tests require any special preparation?
  • How might this condition affect my child?
  • What treatments are available, and which do you recommend?
  • My child has other health conditions. How can we best manage these conditions together?
  • What services are available if my child 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 health care provider will likely ask you several questions. Be ready to answer them to reserve time to go over points you want to focus on. Your health care provider may ask:

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

Your health care provider will ask additional questions based on responses, symptoms and needs. Preparing and anticipating questions will help you make the most of your appointment time.

Content From Mayo Clinic Updated: 02/01/2022
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