Fragile X syndrome: causes, symptoms and treatment

Our genetic code carries the necessary instructions to shape and develop our organism. We inherit much of what we are from our ancestors, although the expression or not of part of these instructions will depend on the environment in which we live.

However, various genetic mutations sometimes occur that can result in the existence of a disorder in those who carry them. This is the case of fragile X syndrome, the second most common cause of mental retardation for genetic reasons.

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Fragile X Syndrome: Description and Typical Symptoms

Fragile X syndrome or Martin-Bell syndrome is an X-linked recessive genetic disorder. The symptoms that this syndrome produces can be observed in different areas.

The most notable are those related to cognition and behavior, although they may present other symptoms such as typical morphological alterations or even metabolic problems. Although it affects both men and women, as a general rule it is much more prevalent in the former, also having a more pronounced and serious symptomatology.

Cognitive and behavioral symptoms

One of the most characteristic symptoms is the presence of intellectual disability. In fact, along with Down syndrome, Fragile X syndrome is one of the most common genetic causes of mental retardation. This disability can be highly variable.

In the case of women, an intelligence level is usually observed at the limit of intellectual disability, with an IQ between 60 and 80. However, in men the level of disability is usually much higher, with an IQ usually between 35 and 45. In this case we would be facing a moderate disability, which would mean a slower and delayed development in the main milestones such as speech, with difficulties in abstraction and the need for a certain level of supervision.

Another frequent aspect is the presence of a high level of hyperactivity, presenting motor agitation and impulsive behaviors. In some cases, they can injure themselves. They also tend to have difficulties concentrating and maintaining attention.

It is also possible that they present typically autistic behaviors, which can lead to the presence of severe difficulties in social interaction, phobia of contact with other people, mannerisms such as shaking hands and avoidance of eye contact.

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Typical morphology

With regard to physical characteristics, one of the most common morphological characteristics in people with fragile X syndrome is that have a certain level of macrocephaly from birth, possessing relatively large and elongated heads. Other common aspects are the presence of large eyebrows and ears, a prominent jaw and forehead.

It is relatively common for them to have hypermobile joints, especially in the extremities, as well as hypotonia or a muscle tone below what is expected. Spinal deviations are also common. Macroorchidism, or excessive testicular development, may also appear in males, especially after adolescence.

Medical complications

Regardless of the types of characteristics that we have seen, people with fragile X syndrome can present alterations such as gastrointestinal problems or decreased visual acuity. Unfortunately, many of them present cardiac alterations, having a greater possibility of suffering heart murmurs. A high percentage, between 5 and 25%, also suffer seizures or epileptic seizures, whether localized or generalized.

Despite this, those with Martin-Bell syndrome they can have a good quality of life, especially if the diagnosis is made early and there is treatment and education that allow the effects of the syndrome to be limited.

Causes of this disorder

As we have indicated, Fragile X syndrome is a genetic disorder linked to the X sex chromosome.

In people with this syndrome, the sex chromosome X suffers a type of mutation which causes a specific series of nucleotides of the FMR1 gene, specifically the Cytosine-Guanine-Guanine (CGG) chain, to appear excessively repeated throughout the gene.

While subjects without such a mutation can have between 45 and 55 repeats of this chain, a subject with Fragile X syndrome can have between 200 and 1300. This prevents the gene from being able to express itself correctly, so it does not produce the FMRP protein as it is silenced.

The fact that the X chromosome is affected by the mutation is the main reason why the disorder is observed more often and with greater severity in men, having only one copy of said chromosome. In women, having two copies of the X chromosome, the effects are minor, and the symptoms may not even appear (although they can transmit it to the offspring).

Martin-Bell syndrome treatment

Fragile X syndrome does not currently have any type of cure. However, the symptoms caused by this disorder can be treated palliatively and in order to improve their quality of life, through a multidisciplinary approach that includes medical, psychological and educational.

Some of the treatments that are used with people with this syndrome in order to improve their quality of life are speech therapy and different speech therapies in order to improve their communication skills, as well as occupational therapy that helps them integrate the information from the different sensory modalities.

Programs and cognitive-behavioral treatments They can be used to help them establish basic and more complex behaviors. At an educational level, it is necessary that they have individualized plans that take into account their characteristics and difficulties.

At the pharmacological level, the SSRI, anticonvulsants and different anxiolytics in order to reduce the symptoms of anxiety, depression, obsession, psychomotor agitation and seizures. Psychostimulant-type drugs are also occasionally used in cases in which there is a low level of activation, as well as atypical antipsychotics in those occasions in which aggressive or self-destructive behaviors tend to occur.

Bibliographic references:

• Grau, C.; Fernández, M. & Cuesta, J.M. (2015). Fragile X syndrome: Behavioral phenotype and learning difficulties. Century Zero, vol. 46 (4), # 256. Editions University of Salamanca.