What Is Triple X Syndrome?

Medically Reviewed by Jabeen Begum, MD on November 25, 2021
4 min read

Most people are born with 46 chromosomes that are divided into 23 pairs. Chromosome pairs carry genes from each parent, which determine a person’s physical characteristics, like their height or eye color. The 23rd pair of chromosomes determine whether a person is born male or female. People who are born female usually have two X chromosomes. 

Triple X syndrome (also called trisomy X syndrome, XXX syndrome, or 47,XXX) is a rare genetic condition where females inherit an extra X chromosome. For some females with triple X syndrome, the third X chromosome can be found in every cell in their body. For others, it is only found in some of their cells.

Triple X syndrome is thought to affect about 1 out of every 1,000 female babies born. This number could potentially be much higher because many women with the condition might not ever be diagnosed if they do not have any obvious physical symptoms or developmental problems.

Here is what you need to know about what causes triple X syndrome, its symptoms, and how it is diagnosed and treated. 

Triple X syndrome is congenital, which means that people with the condition are born with it. It affects only females and happens when an extra X chromosome is inherited.

Women who are over age 35 when their babies are born might have an increased risk of giving birth to a daughter with triple X syndrome. 

Triple X syndrome happens either when there is a problem with the sperm or egg during conception or because of an error in cell division during the embryo’s early stages of development. 

If triple X syndrome happens during early development, the baby might be born with a mosaic form of the condition. Mosaicism happens when some cells have two regular X chromosomes, but others have three. The percentage of cells with three X chromosomes can be different for each person with triple X syndrome. 

Triple X syndrome is random and unpreventable. Even if you have a triple X chromosome, it won't usually be passed down to your children. 

Many girls and women with triple X syndrome have mild symptoms or don’t experience any symptoms at all. People with triple X syndrome that affects all of their cells or a higher percentage of their cells are more likely to have more severe or obvious symptoms.

Triple X syndrome symptoms can include: 

  • Very long legs and above average height
  • Widened space between the eyes
  • Epicanthal folds (skin folds that cover the inner corners of the eyes)
  • Flat feet
  • Curved or bent pinky fingers
  • Abnormal breastbone shape
  • Seizures
  • Malformed kidneys and ovaries
  • Heart irregularities
  • Fertility problems and early ovarian failure
  • Hypothyroidism or other autoimmune conditions

Women and girls with a triple X chromosome also might have a greater risk of developmental, learning, and psychological problems such as:

Sometimes, triple X syndrome is diagnosed when a woman has difficulty getting pregnant or experiences early menopause because of ovarian problems.

During pregnancy, you might be offered non-invasive prenatal testing (NIPT), amniocentesis, or chorionic villi sampling (CVS) to check for a variety of potential genetic problems. These tests can help to diagnose triple X syndrome before your baby is born.

If your doctor suspects a girl or woman might have triple X syndrome, they will ask to take a blood sample to perform a karyotype or chromosome microarray. Both tests diagnose triple X syndrome by showing if an extra X chromosome is present and what percentage of cells are affected. 

There’s no cure for triple X syndrome, so treatment often depends on each person’s symptoms and needs.

If you have triple X syndrome, your doctor might recommend some tests and screenings to check for common health issues caused by the condition. Your doctor might request ultrasounds to look for kidney or ovary issues or an echocardiogram (EKG) to check for heart problems.

Your doctor might suggest estrogen therapy if you are getting excessively tall or experience early menopause from ovarian failure.

Triple X syndrome treatment can also involve special intervention services, counseling, and support for physical, mental, or social problems. This can include:

  • Speech and language therapy
  • Physical therapies
  • Educational assistance for learning disabilities
  • Counseling for anxiety, depression, or behavioral and emotional problems
  • Programs to help improve socialization and daily living
  • Employment assistance
  • Family planning and fertility counseling

Many girls and women with triple X syndrome can lead normal, healthy lives. Regular medical checkups, counseling, and support can play a big role in your overall health and outcome. Talk to your doctor about what treatments you may need if there are any support groups or resources available to people with triple X syndrome in your area.