Fragile X Syndrome

Fragile X syndrome (FXS), also known as the Martin-Bell syndrome, is a genetic condition that causes intellectual disability with lifelong difficulties.

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Definition of Fragile X Syndrome

Fragile X syndrome (FXS), also known as the Martin-Bell syndrome, is a genetic condition that causes intellectual disability with lifelong difficulties. FXS is named Fragile X syndrome because, when looked at through a microscope, part of the X chromosome looks “broken” or “fragile”. This syndrome is genetic, meaning that it is passed down from parents to children. Although Fragile X syndrome can affect both genders, it has been noted to affect males more frequently and with higher severity than in females. The main reason why it’s less prevalent or less severe in females is that some females may not exhibit some features of the Fragile X syndrome e.g., they may not show behavioural, physical or cognitive features of FXS. Also since the gene mutation is X-linked, males are more severely affected than females (CDC, 2001; National Fragile X Foundation; Raspa et al., 2017; & Ray et al., 2017).


Causes of Fragile X Syndrome

Fragile X syndrome is caused by a change to or mutation of a gene on the X-chromosome called the FMR1 gene. This gene produces a protein needed for normal development which helps the brain to function normally. If this gene is changed or altered in any way, it cannot produce its normal protein, which can then lead to Fragile X syndrome. In some rare instances, there is the possibility of those affected may either have the FMRI gene partially or completely missing either having a partially or completely missing.

Fragile X syndrome is inherited in a way that is known as 'X-linked', as the changed gene is on the X chromosome. This means that men with Fragile X syndrome are often more severely affected than women. This is because men only have one X chromosome, whereas women have two X chromosomes, only one of which is changed.


Types of Fragile X Syndrome

There are three main types of Fragile X syndrome disorders caused by changes to the FMRI gene (CDC, 2001; National Fragile X Foundation; Raspa et al., 2017; & Ray et al., 2017). These changes are what scientists usually refer to as mutations. 

  • Fragile X syndrome – this is caused by a full mutation of the FMR1 gene which typically makes a protein the called Fragile X mental retardation protein (FMRP) which is needed for normal brain development. This means that people who are affected are not making the FMRP because the FMRI gene has been turned off, resulting in a full mutation of the gene. 
  • Fragile X-associated primary ovarian insufficiency (FXPOI) – this is the condition where ovarian function is not normal. Those who exhibit this type are due to premutation or excess number of mutations in the FMRI gene. This means those affected by this condition may not have fully functioning ovaries which may lead to early menopause or infertility. 

Fragile X-associated tremor/ataxia syndrome (FXTAS) – this is a neurodegenerative disorder with adult-onset or also referred to as a nervous system disorder that may sometimes lead to tremors and challenges with walking, balance (also called ataxia), memory and mood disorders among older adults.


Symptoms of Fragile X Syndrome

Symptoms of the Fragile X syndrome vary from challenges in physical, behavioural, emotional and developmental aspects of those affected. Behavioural characteristics evident in males may also be evident in females, however, in most instances affected females may exhibit milder intellectual disability, behavioural and physical features of the syndrome. 

Behavioural symptoms:

  • Attention Deficit Hyperactivity Disorder (ADHD)
  • General and social anxiety
  • Autism-like behaviour including hand-biting and/or hand flapping, words and sentence repetition, as well as challenges with social interactions.
  • Poor eye contact
  • Sensory disorders where those affected have challenges in processing sensory information.

Intellectual disabilities and challenges:

  • Delayed development, including challenges with speech, language, and communication.
  • Intellectual disability and learning challenges.

Distinctive physical features: 

  • Some affected males may exhibit signs such as having a protruding forehead, a long narrow face, and/or large testicles (also referred to as “macroorchidism”) in post-pubertal males
  • Unusually large ears
  • Unusually soft skin

Connective tissue complications: 

  • Feet that are, or seem, flat without the middle arch
  • High arched palate
  • Joints that are hyper-flexible 
  • Fingers that are double-jointed

(CDC, 2001; National Fragile X Foundation; Raspa et al., 2017; & Ray et al., 2017)



Centers for Disease Control and Prevention (2021, June 1). Data and Statistics on Fragile X Syndrome. CDC.

National Fragile X Foundation (n.d.). Fragile X 101. National Fragile X Foundation.

Raspa, M., Wheeler, A. C., & Riley, C. (2017). Public Health Literature Review of Fragile X Syndrome. Pediatrics, 139(3), S153-S171. 

Ray, P., Singh, A., Dash, J. K., Sahoo, P. K., & Dash, J. K. (2017). Fragile X Syndrome: A Rare Case Report with Unusual Oral Features. Contemporary Clinical Dentistry, 8(4), 650-652.


Behaviour Help

If you are supporting an individual with this diagnosis, please refer to our services and resources. They aim to help children, adolescents and adults achieve better communication, social, emotional, behavioural and learning outcomes. So whether you are wanting guidance on parenting, teaching, supporting or providing therapy, Behaviour Help is at hand.

Note: This is not an exhaustive list of all the possible causes, symptoms and types but some general information that can be further explored. Based on what you have read if you have any concerns about an individual, please raise them with the individual/s. The caregiver can then raise these concerns with their local doctor who can provide a referral to the relevant professional (e.g. paediatrician, psychologist, psychiatrist, allied health professional and learning specialists) for diagnosis and treatment if appropriate.

Which resources are right for you?


Based on the Taking CHARGE of Rainbow of Emotions Workbook this app helps children of all ages develop emotional regulation skills. The app guides the child to firstly, identify and express their emotion in appropriate ways. Then the child is guided to use emotional management tool/s from the CHARGE tool kit to manage their emotions in a healthy way.

The acronym CHARGE stands for the different categories of emotional management tools – Chat tools, Helpful thinking tools, Amusement tools, Relaxation tools, Good routine tools and Exercise tools.

Behaviour Help App - Using the evidence-based approach of Positive Behaviour Support (PBS), the Behaviour Help web-based app allows people supporting individuals with emotional and behavioural difficulties to complete a Functional Behaviour Analysis and put together a comprehensive Behaviour Support Plan (BSP). The BSP can then be used by everyone interacting with the individual to manage and prevent challenging behaviours and ultimately improve their lives, and the lives of those who support them.


If you want to learn more about emotional and behavioural difficulties then we have a great range of books you can read on your Kindle or order from Amazon.


Personalised and practical one to one help tailored specifically to your family.

Online Courses

Access these online courses anytime online to learn about a range of diagnoses, practical skills and strategies to help develop the individual’s emotional regulation skills. Also learn to utilise the positive behaviour support framework to address anxiety, aggression, ADHD, ASD and ODD.

SEL Educational Videos

Minimise or eliminate the occurrence of challenging behaviours by teaching children of all ages appropriate ways of communicating, interacting, managing their emotions and behaviours.

The SEL curriculum uses video modelling to provide direct, explicit and systematic teaching of the various skills by discussing the importance of the skill, modelling the skill so the child learns what the skill looks like? sounds like? feels like? and learn the skill in staged situations that simulate real life scenarios.


Personalised and practical behaviour therapy tailored specifically to your family.


Webinars discuss a range of practical strategies to guide your child learn positive ways of behaving and managing their emotions.


Attend our practical and interactive workshops to learn about a range of diagnoses, practical skills and strategies to help develop the individual’s emotions, behaviours, social and communication skills in your learning environment.

Ask Dolly

Since you’re here, you probably have questions and concerns. I am Dolly Bhargava, am here to help. I am a NDIS registered behaviour support practitioner and speech pathologist.

I have worked in a number of settings for over 21 years so, how can I help?

Please tell me what is worrying you right now and I will do my best to recommend resources and/or services that will be most useful to you in your situation.

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