Fragile X Syndrome is caused by a mutation in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene, which is located in the X chromosome.
The gene is responsible for synthesising a protein called FMRP. This is responsible for establishing and maintaining connections between the cells in the brain and the nervous system. The mutation causes the body to make only a little or no protein, which often results in the symptoms of Fragile X.
This syndrome is passed down from parents to offspring. Any parent with the FMR1 gene mutation can pass it to their offspring. However, a person inheriting the gene mutation may not develop Fragile X syndrome. Males will pass it down to only their daughters while females have a 50/50 chance to pass it on to their sons and daughters.
Causes
The mutation in the FMR1 gene is referred to as a CGG repeat expansion (size of the mutation). Normally, the FMR1 gene has a specific sequence of three DNA building blocks “cytosine (C), guanine (G), and guanine (G)” repeated a certain number of times. However, in individuals with fragile X syndrome, there is an abnormally high number of CGG repeats in the FMR1 gene.
Fragile X Syndrome is classified into three categories based solely on the size of the mutation.
- Full mutation: This is the most acute form of Fragile X Syndrome. Since the size of the mutation is very high, it results in the gene being silenced. Little or no FMR protein is produced leading to characteristic features and symptoms of Fragile X Syndrome.
- Premutation: People with permutation do not have significant intellectual abilities associated with the syndrome. However, they are at risk of developing some conditions later in life. Such as fragile X-associated tremor/ataxia syndrome (FXTAS) in males and fragile X-associated primary ovarian insufficiency (FXPOI) in females.
- Intermediate/Grey zone mutation: This is still very much under research as it is not well understood. Individuals with these mutations do not exhibit the full range of symptoms for the syndrome.
Symptoms
- Intelligence and learning: People with Fragile X are more likely to have learning disabilities such as dyslexia, dyscalculia, and dysgraphia. These disabilities make reading, writing and math difficult.
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- The syndrome may affect the ability to think, reason, and learn, because of a lower-than-average IQ
- People with Fragile X are more likely to have behavioural problems such as attention deficit hyperactivity disorder (ADHD), anxiety, and aggression. These problems can make it difficult to learn and socialise.
- Physical: Children who hit puberty develop specific features of the syndrome. The features include a narrow face, large head, flexible joints and feet, large ears and forehead. These signs become more obvious with age.
- Behavioural, social and emotional: Some of the challenges they exhibit include anxiety in new situations, and making eye contact. The boys may be aggressive, and attention deficit and the girls shy, attention deficit and hyperactive.
- Sensory: Sensitive to loud noise, bright light, and fabrics on their skin. This causes them to act out or display behaviour problems.
Treatment
There is no cure for Fragile X Syndrome, but treatments are available to manage and minimise the symptoms. Individuals with the syndrome who receive therapy services, medication and suitable education have the best chance of developing individual skills and capabilities.
Early intervention is important. An infant’s brain is malleable and this method gives them the best start and great chance of developing. The sooner the intervention, the better for the child.
Key Reminders
- It is a genetic disorder.
- Nigerian Statistics show it affects 1/4000 boys and 1/8000 girls.
- Its symptoms are more prominent in boys than girls. The reason is that girls have two X chromosomes. If the FMR1 gene on one chromosome has the mutation, the other may not. Even if she has a large size of mutation, the body will still make some FMRP, leading to mild symptoms.
