Table of ContentsView AllTable of ContentsSymptomsCausesDiagnosisTreatmentInheritance and Screening

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Table of Contents

Symptoms

Causes

Diagnosis

Treatment

Inheritance and Screening

Fragile X syndrome is a medical condition that causes intellectual disability and other medical problems. It is the most common kind of genetically inherited intellectual disability, and the second-most common type of intellectual disability overall (afterDown syndrome).

Fragile X syndrome is estimated to occur in about one male in 5,000 to 7,000 and in about one female in 4,000 to 6,000.It is named for the unusual appearance of the X chromosome of people with fragile X syndrome (seen in certain laboratory tests).

This article describes the symptoms of fragile X syndrome, including behavioral symptoms and possible changes in physical appearance. It explains what causes fragile X syndrome and how this condition is diagnosed and treated. It also covers inheritance, related conditions, and screening.

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Symptoms of Fragile X Syndrome

People with fragile X syndrome can have a variety of symptoms that can differ in severity. Not everyone with fragile X syndrome will experience all these potential issues. The problems present and their severity also may change over an individual’s lifetime. One good piece of news is that people with fragile X syndrome appear to have a normal or near-normal life span.

Because of the nature of the genetic problem causing fragile X syndrome, females tend to be less severely affected than males.

Brain and Nervous System

Developmental delay and intellectual disability are major issues in fragile X syndrome. For example, a child might first learn to talk or walk at a much later age than normal.

Some people with fragile X syndrome have normal intellectual functioning. At the other extreme, some people have severe intellectual disability. According to estimates, intellectual disability occurs in about 85% of males and in about 25% of females.

Behavioral issues are another big category. Some of the possible issues include:

Researchers estimate that about 50% of males and 20% of females with fragile X syndrome have anautism spectrum disorderas well.In fact, though autism has many different multi-factorial causes, fragile X syndrome is the most common known cause of the condition. It accounts for about 2–3% of all cases of autism.

General Medical Issues

Some of the medical issues that can occur in people with fragile X syndrome include:

Some people with fragile X syndrome also possess certain characteristic facial features, like a long face with a broad forehead, large ears, and prominent jaw. However, not all people with fragile X syndrome have features like this, and these physical characteristics aren’t always obvious at birth.

Causes of Fragile X Syndrome

Because of a genetic error, the FMR1 gene can’t make FMRP the way it normally would. Most commonly, the genetic error causes an abnormal repeated series of nucleotides (components of DNA) to be inserted in the normal DNA sequence. This specific mutation is called a CGG repeat. In people with fragile X syndrome, this sequence is repeated over 200 times (compared to a normal repeat number of 5 to 44).

Because of this, the FMR1 gene can’t make FMRP protein as it would in someone without fragile X syndrome. In people with fragile X syndrome, the FRMR1 gene doesn’t make any FMR1 protein at all, or it makes it in lower amounts that normal. Individuals who can make some FMRP tend to have less severe symptoms than those who cannot make any functional protein.

FMRP also is present in some other types of cells, like the testes, and lack of the protein in these other parts of the body can lead to other symptoms.

More Genetics

The FMR1 gene is found on the Xchromosome. That’s the sex chromosome, of which females have two copies and males have one copy. In males with fragile X syndrome, only one FRMP gene is available. However, females usually have some copies of the FRMP gene that work normally, because they receive an unaffected X chromosome from one of their parents. That’s why they tend to have fewer and less severe symptoms.

Another factor complicates the understanding of fragile X syndrome. Some people have what is called a “premutation” of the FMR1 gene. This is not a full-blown mutation causing fragile X syndrome, but it isn’t quite normal.

People who have between 55 and 200 CGG repeats in the FMR1 gene have such a “premutation.” Those people may pass fragile X on to their children, and they are at risk of certain medical conditions.

How Fragile X Syndrome Is Diagnosed

Family history is an important part of the diagnostic process, including the history of intellectual disability in the family. However, other family problems might also point toward fragile X syndrome as a possibility. For example, a history of tremor in an older relative might indicate a problem with the FMR1 gene, which might make fragile X syndrome more likely. A relative with early menopause or fertility issues might be another clue.

It’s key that your physician gets a clear idea of all the problems involved. This is critical, since not everyone with fragile X syndrome has identical symptoms. Sometimes these medical problems can provide clues about the underlying cause of the problem. Other times, subtle physical differences can give a clue about the presence of fragile X syndrome.

A variety of tests are sometimes used to help narrow in on a diagnosis. These will depend on the specific symptoms present. Such tests can sometimes rule out other possible causes. For example, a child might receive tests like the following:

Genetic testingis essential for definitive diagnosis. This is done via a specialized genetic test of the FMR1 gene that detects the CGG nucleotide repeat inside the gene. It’s important that clinicians be thinking about the possibility of fragile X syndrome so that they can use this test to confirm the disease. In some cases, even more specialized genetic tests may be necessary to pick up the diagnosis.

It’s important that caregivers of a child provide insights about developmental and behavioral issues. It’s also essential to look for symptoms that might indicate autism.

Detailed tests of intellectual functioning and various psychiatric tests can also provide insight (e.g., IQ tests).These can help give an idea of the individual’s needs and potentials, as well as the types of interventions that might help. Often, specialists can aid in these assessments.

Treatment for Fragile X Syndrome

Currently, no specific treatment is available to address the root causes of fragile X syndrome.However, a team of medical professionals will help your loved one receive the best possible support and care.

Working with people who have specialized training in childhood genetic diseases like fragile X syndrome can be extremely beneficial. It’s important that infants with fragile X syndrome receive referrals to early intervention programs, which can provide support in a child’s development.

Treatment of fragile X syndrome requires work from a variety of specialists. For example, some of the following are often helpful:

These therapies can help an individual with fragile X manage some of their symptoms and maximize their quality of life.

As children with fragile X become old enough to enter preschool and school, they will need formalized evaluation for specifically tailored therapies and services. This is written up in something called an individualized education plan (IEP). This provides a plan so that children with fragile x syndrome can receive the best support while also being included in general education to the extent that is possible.

Sometimes, medications are helpful for some of the problems of fragile X syndrome. For example, depending on the circumstances, this might include:

Regular monitoring is also an essential part of ongoing care. For example, your healthcare provider will need to monitor for the development of potential heart problems, like mitral valve prolapse.

Additionally, it’s helpful to network with other families. TheNational Fragile X Foundationprovides much helpful support, advocacy, and information for families dealing with a fragile X syndrome diagnosis.

Fragile X syndrome is an inherited condition, meaning it is passed down from your biological parents. The same gene involved in fragile X syndrome can cause associated disorders. Genetic screening can be used to identified people who are affected.

Inheritance

Thegenetic inheritanceof fragile X syndrome is quite complicated and unusual. Talk to a genetic counselor about your specific situation and see whether you might need to get genetic testing yourself.

Genetic testing is particularly important because having a person with fragile X syndrome in the family might mean you’re at risk of certain health conditions.You may need to get tested even if you have no plans of having a child.

Fragile X syndrome follows most of the patterns of what is called an X-linked dominant disorder. X-linked means the gene that causes the disorder is located on the X chromosome, and dominant means one copy of the gene is enough to cause the condition.

Something else complicates the inheritance of fragile X syndrome—premutations. People with premutations don’t have fragile X syndrome, and they may not have any medical problems at all.

However, people with premutations are at risk of having certain other medical problems. One is a medical condition called fragile X-associated tremor/ataxia syndrome (FXTAS), which leads to tremor and difficulty with balance later in life.

Females with premutations are at risk of another medical condition called fragile-X associated primary ovarian insufficiency (FXPOI). This can causepremature menopauseor early ovarian failure.

Additionally, a premutation can be a concern because sometimes it will be transmitted to children as a full mutation.In that case, a child might get fragile X syndrome from a parent even though neither parent has fragile X syndrome.

Screening and Prenatal Counseling

The American Congress of Obstetricians and Gynecologists recommends genetic counseling and screening for fragile X for all females who have a personal or family history of the disease. They also recommend it for females who have a personal or family history of unexplained intellectual disability, autism, or ovarian insufficiency before the age of 40.

It’s important to get tested to understand your own medical risks as well as those of any potential offspring.

Prenatal diagnosis may be possible for people known to be carriers of the FMR1 gene mutation. It may also be possible to use in vitro fertilization and preimplantation services to ensure the conception of children without the condition.

Summary

Fragile X syndrome is a genetic condition resulting in mutations on the X chromosome. It can cause several symptoms, including developmental problems, behavioral symptoms, and changes in physical appearance.

Talk to a healthcare provider if you suspect fragile X syndrome in a child or yourself. Healthcare providers can test for this genetic mutation to identify people who have fragile X syndrome and who could pass it on to their children.

There is no specific treatment for fragile X syndrome, but there are treatment options to help people with fragile X syndrome manage symptoms and develop skills.

12 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Ciaccio C, Fontana L, Milani D, Tabano S, Miozzo M, Esposito S.Fragile X syndrome: a review of clinical and molecular diagnoses.Ital J Pediatr. 2017;43(1):39. doi:10.1186/s13052-017-0355-ySalcedo-Arellano MJ, Dufour B, McLennan Y, Martinez-Cerdeno V, Hagerman R.Fragile X syndrome and associated disorders: clinical aspects and pathology.Neurobiol Dis. 2020;136:104740. doi:10.1016/j.nbd.2020.104740MedlinePlus.Fragile X syndrome.Lozano R, Azarang A, Wilaisakditipakorn T, Hagerman RJ.Fragile X syndrome: a review of clinical management.Intractable Rare Dis Res. 2016;5(3):145–157. doi:10.5582/irdr.2016.01048Kaufmann WE, Kidd SA, Andrews HF, et al.Autism spectrum disorder in fragile X syndrome: cooccurring conditions and current treatment.Pediatrics. 2017;139(Suppl 3):S194–S206. doi:10.1542/peds.2016-1159FHunter JE, Berry-Kravis E, Hipp H, et al.FMR1 disorders. GeneReviews.Centers for Disease Control and Prevention.How fragile X syndrome is inherited.Richter JD, Zhao X.The molecular biology of FMRP: new insights into fragile X syndrome.Nat Rev Neurosci. 2021;22(4):209-222. doi:10.1038/s41583-021-00432-0Tassone F, Hagerman PJ, Hagerman RJ.Fragile X premutation.J Neurodev Disord. 2014;6(1):22. doi:10.1186/1866-1955-6-22Kishore MT, Udipi GA, Seshadri SP.Clinical practice guidelines for assessment and management of intellectual disability.Indian J Psychiatry. 2019;61(Suppl 2):194-210. doi:10.4103/psychiatry.IndianJPsychiatry_507_18Biancalana V, Glaeser D, McQuaid S, Steinbach P.EMQN best practice guidelines for the molecular genetic testing and reporting of fragile X syndrome and other fragile X-associated disorders.Eur J Hum Genet. 2015;23(4):417-25. doi:10.1038/ejhg.2014.185The American College of Obstetricians and Gynecologists.Carrier screening for genetic conditions.

12 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Ciaccio C, Fontana L, Milani D, Tabano S, Miozzo M, Esposito S.Fragile X syndrome: a review of clinical and molecular diagnoses.Ital J Pediatr. 2017;43(1):39. doi:10.1186/s13052-017-0355-ySalcedo-Arellano MJ, Dufour B, McLennan Y, Martinez-Cerdeno V, Hagerman R.Fragile X syndrome and associated disorders: clinical aspects and pathology.Neurobiol Dis. 2020;136:104740. doi:10.1016/j.nbd.2020.104740MedlinePlus.Fragile X syndrome.Lozano R, Azarang A, Wilaisakditipakorn T, Hagerman RJ.Fragile X syndrome: a review of clinical management.Intractable Rare Dis Res. 2016;5(3):145–157. doi:10.5582/irdr.2016.01048Kaufmann WE, Kidd SA, Andrews HF, et al.Autism spectrum disorder in fragile X syndrome: cooccurring conditions and current treatment.Pediatrics. 2017;139(Suppl 3):S194–S206. doi:10.1542/peds.2016-1159FHunter JE, Berry-Kravis E, Hipp H, et al.FMR1 disorders. GeneReviews.Centers for Disease Control and Prevention.How fragile X syndrome is inherited.Richter JD, Zhao X.The molecular biology of FMRP: new insights into fragile X syndrome.Nat Rev Neurosci. 2021;22(4):209-222. doi:10.1038/s41583-021-00432-0Tassone F, Hagerman PJ, Hagerman RJ.Fragile X premutation.J Neurodev Disord. 2014;6(1):22. doi:10.1186/1866-1955-6-22Kishore MT, Udipi GA, Seshadri SP.Clinical practice guidelines for assessment and management of intellectual disability.Indian J Psychiatry. 2019;61(Suppl 2):194-210. doi:10.4103/psychiatry.IndianJPsychiatry_507_18Biancalana V, Glaeser D, McQuaid S, Steinbach P.EMQN best practice guidelines for the molecular genetic testing and reporting of fragile X syndrome and other fragile X-associated disorders.Eur J Hum Genet. 2015;23(4):417-25. doi:10.1038/ejhg.2014.185The American College of Obstetricians and Gynecologists.Carrier screening for genetic conditions.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Ciaccio C, Fontana L, Milani D, Tabano S, Miozzo M, Esposito S.Fragile X syndrome: a review of clinical and molecular diagnoses.Ital J Pediatr. 2017;43(1):39. doi:10.1186/s13052-017-0355-ySalcedo-Arellano MJ, Dufour B, McLennan Y, Martinez-Cerdeno V, Hagerman R.Fragile X syndrome and associated disorders: clinical aspects and pathology.Neurobiol Dis. 2020;136:104740. doi:10.1016/j.nbd.2020.104740MedlinePlus.Fragile X syndrome.Lozano R, Azarang A, Wilaisakditipakorn T, Hagerman RJ.Fragile X syndrome: a review of clinical management.Intractable Rare Dis Res. 2016;5(3):145–157. doi:10.5582/irdr.2016.01048Kaufmann WE, Kidd SA, Andrews HF, et al.Autism spectrum disorder in fragile X syndrome: cooccurring conditions and current treatment.Pediatrics. 2017;139(Suppl 3):S194–S206. doi:10.1542/peds.2016-1159FHunter JE, Berry-Kravis E, Hipp H, et al.FMR1 disorders. GeneReviews.Centers for Disease Control and Prevention.How fragile X syndrome is inherited.Richter JD, Zhao X.The molecular biology of FMRP: new insights into fragile X syndrome.Nat Rev Neurosci. 2021;22(4):209-222. doi:10.1038/s41583-021-00432-0Tassone F, Hagerman PJ, Hagerman RJ.Fragile X premutation.J Neurodev Disord. 2014;6(1):22. doi:10.1186/1866-1955-6-22Kishore MT, Udipi GA, Seshadri SP.Clinical practice guidelines for assessment and management of intellectual disability.Indian J Psychiatry. 2019;61(Suppl 2):194-210. doi:10.4103/psychiatry.IndianJPsychiatry_507_18Biancalana V, Glaeser D, McQuaid S, Steinbach P.EMQN best practice guidelines for the molecular genetic testing and reporting of fragile X syndrome and other fragile X-associated disorders.Eur J Hum Genet. 2015;23(4):417-25. doi:10.1038/ejhg.2014.185The American College of Obstetricians and Gynecologists.Carrier screening for genetic conditions.

Ciaccio C, Fontana L, Milani D, Tabano S, Miozzo M, Esposito S.Fragile X syndrome: a review of clinical and molecular diagnoses.Ital J Pediatr. 2017;43(1):39. doi:10.1186/s13052-017-0355-y

Salcedo-Arellano MJ, Dufour B, McLennan Y, Martinez-Cerdeno V, Hagerman R.Fragile X syndrome and associated disorders: clinical aspects and pathology.Neurobiol Dis. 2020;136:104740. doi:10.1016/j.nbd.2020.104740

MedlinePlus.Fragile X syndrome.

Lozano R, Azarang A, Wilaisakditipakorn T, Hagerman RJ.Fragile X syndrome: a review of clinical management.Intractable Rare Dis Res. 2016;5(3):145–157. doi:10.5582/irdr.2016.01048

Kaufmann WE, Kidd SA, Andrews HF, et al.Autism spectrum disorder in fragile X syndrome: cooccurring conditions and current treatment.Pediatrics. 2017;139(Suppl 3):S194–S206. doi:10.1542/peds.2016-1159F

Hunter JE, Berry-Kravis E, Hipp H, et al.FMR1 disorders. GeneReviews.

Centers for Disease Control and Prevention.How fragile X syndrome is inherited.

Richter JD, Zhao X.The molecular biology of FMRP: new insights into fragile X syndrome.Nat Rev Neurosci. 2021;22(4):209-222. doi:10.1038/s41583-021-00432-0

Tassone F, Hagerman PJ, Hagerman RJ.Fragile X premutation.J Neurodev Disord. 2014;6(1):22. doi:10.1186/1866-1955-6-22

Kishore MT, Udipi GA, Seshadri SP.Clinical practice guidelines for assessment and management of intellectual disability.Indian J Psychiatry. 2019;61(Suppl 2):194-210. doi:10.4103/psychiatry.IndianJPsychiatry_507_18

Biancalana V, Glaeser D, McQuaid S, Steinbach P.EMQN best practice guidelines for the molecular genetic testing and reporting of fragile X syndrome and other fragile X-associated disorders.Eur J Hum Genet. 2015;23(4):417-25. doi:10.1038/ejhg.2014.185

The American College of Obstetricians and Gynecologists.Carrier screening for genetic conditions.

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