Fragile X syndrome

The commonest inherited cause of learning disability, and the commonest single-gene cause of autism.

What it is

Fragile X is caused by a change in the FMR1 gene on the X chromosome, which stops the body making a protein the brain needs to build connections properly.

Because it is X-linked, boys are usually affected more severely than girls. It affects roughly 1 in 4,000 boys and 1 in 6,000 girls.

It brings a learning disability of varying degree, a strong overlap with autism, and a very characteristic anxiety profile that is worth understanding on its own terms.

Signs you might notice

Learning disability, often with better verbal imitation than comprehension.

Intense social anxiety with a distinctive pattern: wanting contact and avoiding eye gaze at the same time.

Sensory hypersensitivity, particularly to noise and crowds.

Hand-flapping and hand-biting when overwhelmed.

Physically: a longer face, prominent ears, hypermobile joints, and in boys, enlarged testes after puberty.

How it can affect day-to-day life

Anxiety, not the learning disability, is usually what limits a person's day. A person with Fragile X may cope with a supermarket on Tuesday and not on Wednesday, and the difference is arousal, not willingness.

Transitions and unpredictability are the reliable triggers.

Female carriers can be affected too, and adult carriers of the premutation have a raised risk of a tremor and ataxia syndrome (FXTAS) and of early menopause. That is genuinely useful family information and it is regularly not passed on.

Supporting someone well

Reduce arousal before you ask for anything. Quiet, low light, no direct eye contact demand, and give the person time.

Use side-by-side rather than face-to-face for difficult conversations. It works, and it is easy.

Keep routine predictable and warn about change.

Use visual supports and give processing time.

Never demand eye contact. It raises anxiety and produces exactly the behaviour people are trying to reduce.

Refer the family to genetic counselling. This one has implications for siblings and for the wider family.

Fiducia Talk and Fiducia Life between them give a low-demand route into communicating and a predictable daily structure, both of which lower arousal rather than adding to it.

Where to get help

Diagnosis is by a genetic blood test. Ask a GP or paediatrician for referral to clinical genetics.

The Fragile X Society have family support and clear guidance for schools.

Ask for the annual learning disability health check from age 14.