Fragile X syndrome (FXS) or Martin Bell Syndrome (MBS) causes intellectual disability, behavioral problems, and physical abnormalities

Fragile X syndrome (FXS) or Martin Bell Syndrome (MBS) causes intellectual disability, behavioral problems, and physical abnormalities

Fragile X syndrome

Fragile X syndrome is a genetic disease that most commonly causes intellectual disability, behavioral problems, and physical abnormalities. Symptoms vary widely from patient to patient. The syndrome is also referred to as Martin Bell Syndrome (MBS) or Marker X syndrome.

Physical characteristics

It can give physical characteristics like an elongated face, large and prominent and large ears, hyperextensibility of the finger joints, flat feet, large testicles (macro-orchid). It causes very variable intellectual difficulties with moderate to severe cognitive delay. We find behavioral characteristics close to autism with stereotypical movements and social anxiety. Girls affected by this disease are affected in various ways, usually with moderate cognitive delay.


We speak of fragile X syndrome in reference to an anomaly of part of the DNA (molecule carrying hereditary genetic information and having all the information useful for the proper functioning of the organism) located at the level of the gene (DNA segment) FMR1 of the X chromosome (part made up of DNA molecules).

The X chromosome is a sex chromosome, in other words, it is used to determine the sex of an individual. Men have one X chromosome and one Y chromosome, while women have 2 X chromosomes and no Y chromosomes.

The FMR1 gene involved in the disease normally produces the FMRP protein. The latter has many functions that contribute to the proper functioning of the body. One of these functions is to connect nerve cells. However, a person with fragile X syndrome has undergone a change in their DNA which results in an absence of production of the protein FMRP, and which explains the manifestations of the disease.

Main areas of difficulty for the people who have Fragile X syndrome

The main characteristics of Fragile X Syndrome are difficulties with study and behavior.

Among the greatest academic difficulties, especially among boys, we note:

  • language delay or unusual ways of speaking;
  • delay in language acquisition and repetitive language (verbal perseverance);
  • poor short- and long-term memory for abstract information, such as mental arithmetic (eg, 2 x 6), which often leads to math anxiety;
  • lack of spatial orientation and visual-motor coordination, which makes children with fragile X syndrome appear awkward and clumsy;
  • difficulty maintaining attention for a long period of time for tasks that require abstract reasoning, such as math;
    extreme difficulty in performing sequential tasks, such as solving equations;
  • great predisposition to be distracted in class by sudden noises; transitional movements and habits when concentrating on a given task.

Some of the biggest behavioral difficulties include:

  • feeling overwhelmed by the demands of social participation, new or unexpected situations, and even common transitions in everyday life
  • attention deficit hyperactivity disorder, the severity of which often leads to a clinical diagnosis of Attention Deficit Hyperactivity Disorder (ADHD)
  • social avoidance and anxiety;
  • characteristics similar to those of autism.

Autism vs. Fragile X Syndrome

Common points

According to current research, 15 to 25% of children with fragile X syndrome are misdiagnosed with autism, due to the characteristics common to these two disorders:

  • language delays, echolalia and verbal perseverance (repetition);
  • avoidance of eye contact;
  • stereotypical movements, including biting and clapping hands;
  • hypersensitivity to environmental stimuli such as sudden noises (eg, sirens or alarms), movement, or changes in habits, such as transitions from one school activity to another. Anxiety caused by sensory hypertension can often lead to hyperactivity, which in turn can lead to a surge of aggression.
    Important differences

It goes without saying that an erroneous diagnosis made for a child suffering from Fragile X syndrome denies him access to resources and support systems appropriate to his condition and from which he could undoubtedly benefit, particularly in its early school years, when early intervention is most effective. The physical characteristics as well as the social, behavioral and academic disabilities present in people with fragile X syndrome differ from those seen in autistic people. Recognizing these characteristics is crucial to help clinicians properly diagnose the syndrome as early as possible, so that educational and clinical interventions can be implemented from an early age in the child.

Physical characteristics

The physical features that characterize this disorder are an elongated face, a broad forehead and large, prominent ears, and, in boys, macroorchidism (large testes) after puberty. However, given the great variability of manifestations in boys and girls, it is almost impossible to make a diagnosis based solely on physical features. It is precisely because of their “normal” appearance that many children with fragile X syndrome do not receive the correct diagnosis until relatively late in their development.

Social disabilities

Unlike students with autism who often have difficulty establishing relationships with others and understanding the concept of emotions and empathy, children with fragile X syndrome often express a desire to communicate and bond. relationships. Their relationships can, however, be hampered by extreme initial shyness. Once they begin to feel comfortable with their social partners, social relationships from an early age can be quite rich and productive for children with fragile X syndrome. Second, while students with autism have serious difficulty understanding the intentions and beliefs of others, those with Fragile X syndrome have a greater potential for acquiring relatively good skills related to the “theory of”. the mind “. The “theory of mind” is the ability to understand the beliefs and intentions of others.

Main strengths of children with fragile X syndrome:
  • good verbal skills, for example especially the vocabulary understood and expressed;
  • well-developed verbal comprehension and labeling skills;
  • good short- and long-term memory of important information (eg, stories, objects, names) and a particular ability to tap into a repertoire of acquired knowledge and vocabulary;
  • strong visual memory. Students with fragile X syndrome also have good face and emotion recognition skills;
  • ability to concentrate for long periods of time without being too distracted or overly excited, especially if an activity is meaningful and not sequential.
  • ability to focus on computer-based learning techniques.


Fragile X syndrome results in unspecific symptoms that vary widely from patient to patient.

Intelligence, learning, behavior, and even emotions are directly related to the activity of neurons and the connections they have. These connections allow them to communicate with each other. The FMRP protein, absent in patients with fragile X syndrome, appears to be involved in the functioning of neuronal connections, but also in the maintenance properties of connective tissues (thus explaining the hyperlaxity of the joints observed in these patients).

Most often, the first symptom is a delay in the child’s development. It may be visible when learning to walk, or during language development. Behavioral disorders can also be associated resulting, for example, in agitation or avoidance of gaze. Finally, some physical signs may be visible, especially in boys.

In boys

Infants with fragile X syndrome usually do not have any symptoms. Sometimes psychomotor disorders are observed such as:

  • Muscle weakness: the baby holds his head badly, or he sits / walks later;
  • Language delay, or even incomprehensible language at first (up to about 4 years);
  • Difficulty falling asleep or waking up at night;
  • Gastroesophageal reflux disease and ear infections are more common.

Intellectual deficit is most noticeable in childhood. Intellectual abilities can be assessed by tests (determination of IQ). In the general population, the IQ is between 70 and 130. When the IQ is below 70, we speak of intellectual deficit. This deficit implies difficulties in thinking, reasoning and learning for the child. In 10% of cases, small patients do not have an intellectual deficit, but suffer from anxiety and difficulty concentrating which also impact their learning. Language disorders become more noticeable as you get older. They are manifested by difficulty speaking, especially in coordinating the volume, tone and rhythm of the voice. Stuttering can appear with age. Interpretation of other people’s words can also be disrupted with difficulty deciphering facial expressions, tone of voice or body language. Writing disorders can be associated.

All of these symptoms are mainly due to problems with comprehension and memory, especially short-term memory. The child may also have behavioral problems:

  • Inability to look anyone in the eye;
  • Repetition of certain gestures or certain words;
  • Impulsiveness;
  • Hyperactivity;
  • Mood swings ;
  • Irritability;
  • Inattention
  • Anxiety.

Other disorders can also occur:

  • Difficulty doing certain gestures (holding a pencil, dressing);
  • Visual disturbances;
  • Repeated otitis or sinusitis;
  • Hyperlaxity of the joints;
  • Epileptic attacks.
  • In adolescence and later in adulthood, the symptoms of childhood persist, but do not get worse. Behavioral problems, especially hyperactivity, seem to get better as you get older.

Some patients have special physical characteristics that become visible from adolescence onwards: a broad forehead, an elongated face or jaw, ringed eyes and large ears. After puberty, the bursae and testicles may become larger in some patients, causing pain and itching.

In girls

Girls tend to have less severe symptoms than boys. 50% of them also have no symptoms. This is because a male individual only has one X chromosome, so when this one is affected by the abnormality, the FMRP protein is not produced at all, and symptoms appear. . Girls have 2 X chromosomes, so when one of them is affected, the second is unharmed. In each cell of the body, only one X chromosome is used, and the choice of which chromosome to use is random and definitive. Thus, in some cells, the FMRP protein is present, and in others not. If enough cells are producing the FMRP protein normally, then symptoms are mild or absent.

Girls with disorders may have a slightly lower IQ than normal. In most cases, patients do not have significant language impairment. Their main difficulties relate to learning, especially mathematics.

Behavioral problems are also less visible than in boys. Some can be overactive. They tend to be shy, anxious or even depressed and present Obsessive–compulsive disorder (OCD) is a mental and behavioral disorder in which a person has certain thoughts repeatedly (called “obsessions”) and/or feels the need to perform certain routines repeatedly (called “compulsions”) to an extent that generates distress or impairs general functioning. For i.e. cleaning hands, washing dises manually many times.

Autism | Definition, Causes, Symptoms and Management (Pervasive Developmental Disorders (PDD)


Only by looking at the manifestations of the disease is not sufficient to diagnose fragile X syndrome. A genetic test should be performed that is based on analysis of the offending FMR1 gene. The latter is carried out on a simple blood test.

DNA tests
Fragile X syndrome is often not suspected until school age or adolescence, depending on the severity of symptoms, unless there is a significant family history. Boys with autism and intellectual disabilities should be tested for fragile X syndrome, especially when they have maternal family members who are also affected. DNA molecular analysis is performed to detect the increase in the number of CGG repeats.

The Genetic Testing Registry (GTR) provides information about the labs that offer genetic testing for fragile X syndrome. The intended audience for the GTR is health care providers and researchers. People with questions about genetic testing should speak with a health care provider or doctor or genetics professional.

Additional assessments are necessary to assess the severity of the disease and decide on the most appropriate treatment:

A general assessment of the child’s development by a pediatric neurologist;
A speech therapist check-up;
An assessment of intellectual skills by a psychologist.
Other medical examinations may be ordered as appropriate, for example a cardiac ultrasound if there is a suspicion of a cardiac abnormality.


There is currently no treatment for fragile X syndrome. On the other hand, care adapted to intellectual, language or behavioral difficulties must be put in place as soon as the diagnosis is made. Various health professionals can intervene and cooperate with each other.

Early management by speech-language pathologists and occupational therapists can be helpful in children with Fragile X syndrome and help maximize their abilities.

Stimulants, antidepressants, and anti-anxiety medications may be of benefit in some children.

Diseases | List of Diseases: dermatological, cardiovascular, respiratory, cancer, eye, genetic, infectious, mental illness, rare

Information: Cleverly Smart is not a substitute for a doctor. Always consult a doctor to treat your health condition.

Sources: PinterPandai, MedlinePlus, Centers for Disease Control and Prevention (CDC), HealthLine

Photo credit: Photo montage: Wikimedia Commons / PinterPandai 1. Wikimedia Commons 2. Peter Saxon / Wikimedia Commons 3. Peter Saxon / Wikimedia Commons

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