Fragile X syndrome (Martin-Bell syndrome)

Fragile X is the most common genetically inherited condition which causes learning disability. There is a change (mutation) in one of the genes on the X chromosome, which produces a protein essential for brain development.

Fragile X was first described in its classical form in 1943 by Martin and Bell (it is also known as Martin-Bell syndrome), although it was not associated with developmental and behavioural conditions until 1977. It can be accompanied with learning, attention, social, behavioural and language difficulties.


How many people are affected?

Fragile X is diagnosed through a blood test and is estimated to affect around 1 in 4,000 males and 1 in 6,000 females across all races and ethnic groups.

Boys tend to be affected more severely than girls as they have only one X chromosome, while girls have a second X chromosome which can balance out the impact of a faulty one to some extent.
Both men and women can carry Fragile X Syndrome, and within families the condition can affect either multiple generations or just one individual.

As already stated, it is the most common inherited cause of learning disabilities, with 3-4% of children with learning disabilities having Fragile X. The role of genetic counselling is important for families where there is a child with Fragile X.

How it affects people

The main effect of Fragile X is cognitive impairment, which can range from very severe to mild in affected males. Cognitive impairment in females is usually milder.

Fragile X can produce some characteristic physical features, including a long face, prominent ears, and flat feet. Behavioural problems are also often present, with affected individuals tending to exhibit some similarities to people with autism. These similarities can include eye gaze avoidance, social anxiety, repetitive speech errors, and attention deficit disorder.

There are currently no specific treatments for Fragile X syndrome, and there is no known cure.  Some therapies may, however, yield significant benefits. Children experiencing difficulties in communicating can be helped to develop these skills by a speech and language therapist, and behavioural therapy can help with issues such as the development of social skills, and in dealing with hyperactivity.