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Fragile X syndrome

7-minute read

Key facts

  • Fragile X is the most common inherited cause of intellectual disability, and also the most common genetic cause of autism.
  • It is caused by a faulty gene in one of your X chromosomes.
  • Symptoms of fragile X syndrome include speech and language delays, intellectual disabilities and learning difficulties, as well as behavioural and emotional problems.
  • Fragile X is diagnosed with a genetic test. Genetic testing can be done prior to or during pregnancy.
  • Fragile X has no cure, but there are effective treatments.

What is fragile X syndrome?

Fragile X syndrome gets its name from the X chromosome — 1 of the 2 chromosomes that determine your sex at the time of conception. Chromosomes carry DNA (deoxyribose nucleic acid). A gene is a small section of that DNA and contains the chemical information for our inherited characteristics. Sometimes, the X chromosome develops a fault — its DNA changes or mutates.

People can be carriers of this faulty gene without having any symptoms, while others will be born with symptoms of fragile X syndrome.

Fragile X syndrome is more common and more severe in males than in females. This is because males have one X chromosome and one Y chromosome, so if they have a mutation on their X chromosome, they will not have any functioning copies of the fragile X gene. Females have two X chromosomes, so even if they carry the fragile X mutation, they will usually have one functioning copy of the gene on their other X chromosome.

People with fragile X syndrome have intellectual disability, behavioural and learning difficulties, as well as certain physical characteristics. Fragile X syndrome is the most common inherited cause of intellectual disability, and also the most common genetic cause of autism.

It affects around 1 in 3600 males and around 1 in 6000 females.

What are the symptoms of fragile X syndrome?

Some people with fragile X have very few symptoms, while others have significant health problems. The main symptoms of fragile X syndrome are:

People with fragile X syndrome may also have behavioural and emotional problems including:

Females with fragile X syndrome or who carry the gene might experience early menopause.

Male carriers (and occasionally females) might experience fragile X tremor ataxia syndrome. The symptoms are similar to those of Parkinson’s disease and include unsteadiness (ataxia), intention tremor (shaking) and memory problems.

How do I know if I am a carrier for fragile X?

If you have a family history of fragile X, you can be tested before becoming pregnant to see if you are a carrier of the gene for fragile X. If you are a carrier, there is a chance that you can pass the gene on to your children.

Even if you don’t have a family history of fragile X, you can still do a genetic test to find out if you are a carrier for the condition.

If you are a carrier of the fragile X gene, a genetic counsellor can help you explore ways of having a healthy baby.

Can fragile X syndrome be detected during pregnancy?

If you are a known carrier for fragile X, your baby can be tested in pregnancy using amniocentesis or chorionic villous sampling.

If your baby is found to have fragile X, you will need to decide whether to continue with the pregnancy or consider a termination. Your doctor can refer you to a genetic counsellor who specialises in helping people in your situation. You can also call Pregnancy, Birth and Baby for advice and support.

What if my child has fragile X syndrome?

If you have a child of any age showing symptoms of fragile X syndrome, your doctor can ask for a DNA blood test to see if they have the condition. Having a diagnosis can help your child get the help they need.

It can be overwhelming to receive a diagnosis of fragile X syndrome. It’s a good idea to think about seeking support from family or friends as you process the diagnosis.

It’s a good idea to find out as much as you can about fragile X syndrome. The The Fragile X Association of Australia provides information and real-life stories about living with this condition.

There is no cure for fragile X but there are effective treatments for problems your child may experience. You can help your child reach their potential by getting them help as soon as possible after diagnosis. This is called early intervention. A team of different specialists work together to look after your child’s educational, behavioural and medical needs. This team may also include a psychologist to help your family work through some of the difficulties of living with a person with a disability.

Where can I get more information about fragile X syndrome?

Raising a child with a disability is not easy, but help is available.

  • Call the Carer Gateway on 1800 422 737 for support and services.
  • The Fragile X Association has a helpline on 1300 394 636 and provides advice on treatments and early intervention.

Speak to a maternal child health nurse

Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available 7am to midnight (AET), 7 days a week.

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Last reviewed: October 2022

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Need more information?

Fragile X syndrome - Better Health Channel

The facts about fragile X syndrome are complicated, and parents and family members are invited to ask their doctor to refer them to a genetics clinic.

Read more on Better Health Channel website

Fragile X syndrome in children | Raising Children Network

Fragile X syndrome causes intellectual disability and other challenges. Early intervention and support helps children with Fragile X explore their abilities.

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Genetic carrier screening

Screening for carrier status is a blood test to see if you carry genes that are linked to certain health conditions. Learn more about this test here.

Read more on Pregnancy, Birth & Baby website

Fragile X gene | Pathology Tests Explained

Fragile X CGG repeat sizing is routinely performed using a polymerase chain reaction (PCR) method with fluorescently labelled primers. The labelled pieces of

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Pregnancy tests amniocentesis - Better Health Channel

Amniocentesis is a prenatal procedure performed on a pregnant woman to withdraw a small amount of amniotic fluid from the sac surrounding the fetus.

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Genetic counselling

Genetic counselling may be recommended for people who have a history of hereditary disorders. Find out when genetic counselling can be helpful and what to expect.

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What is a congenital disorder?

Congenital disorder, also known as congenital disease or birth defects, are conditions present from birth. Find out more about congenital disorders.

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Birth differences (congenital anomalies)

Health problems present from birth include any health condition that a baby is born with and are sometimes called birth defects, birth differences or congenital anomalies.

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Genomics explainer: genetic inheritance | Garvan Institute of Medical Research

Inheritance patterns describe how genetic variants are distributed in families. Understanding these patterns is crucial to predicting disease risk in family members of an affected individual.

Read more on Garvan Institute of Medical Research website

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