All About Fragile X Chromosomal Disorder

A Common Cause of Developmental Disabilities

Chromosomes. Getty Images Credit: Sandra Baker

Fragile X is the most common known inherited cause of developmental disabilities. Here's what to know about this chromosomal disorder that affects more men than women.

What is Fragile X?

The name "fragile X" comes from the way the X chromosome looks under a microscope: the tip shows an abnormal gap that appears broken, called a fragile site. Studies estimate that around one in 2,000 males and roughly one in 4,000 females of all races and ethnic groups are affected.

Furthermore, one in 800 men and one in 259 women of all races are carriers of fragile X. It is believed that this common genetic defect has yet to be diagnosed in 80 percent to 90 percent of people with the syndrome.

Fragile X is caused by an abnormality involving a single gene called FMR-1, which is situated on the X chromosome. There is an increase in size and some stretching in part of the gene, which affects the way it works. Some men and women who have only a small expansion or stretch show no symptoms, though they are carriers of fragile x (meaning they can pass it on to their children).

Common Symptoms of Fragile X

A person with fragile X can exhibit few or many of the symptoms associated with this disorder. Symptoms include:

  • Intellectual impairment ranging from no abnormality to mild learning difficulties to severe learning disabilities
  • Attention problems, such as problems concentrating on a task
  • Hyperactivity
  • Apparent over-stimulation to external stimuli, such as traffic noise
  • Anxiety
  • Inability to cope with change of a routine
  • Problems relating to others
  • Displaying autism-like behaviors, such as social anxiety, hand flapping, biting and gaze aversion
  • Unstable moods
  • Aggression and depression, particularly in adolescence
  • Problems with hand/eye coordination
  • Difficulty with speech and language; echolalia (repeating words and phrases), jocular speech and up and down swings of pitch (litanic speech), palilalia (repeating the end of phrases they themselves have spoken over and over again)

Physical Characteristics of Fragile X

Physical characteristics of fragile X are noticeable after the onset of puberty. They include:

  • Long face with a prominent jaw
  • Prominent ears
  • Large testicles, mostly after puberty

People with fragile X also are more prone to certain diseases. These include connective tissue problems, including flat feet, loose joints, congenital hip dislocation, scoliosis (curvature of the spine), mitral valve prolapsed (heart valve), and eye problems such as being cross-eyed (strabismus) and squinting.

How Is Fragile X Diagnosed?

Fragile X can be diagnosed by analyzing a person's blood for the FMR1 gene. This DNA test, available since the gene was first identified in 1991, can detect fragile X in normal carriers and in those affected. A doctor cannot tell if a child is or will be intellectually impaired, or the severity of many of the symptoms, from this analysis, however.

How Is Fragile X Treated?

There is currently no cure for fragile X, but once it has been diagnosed, there are a number of strategies that can help many children and adults.

It is important that a multidisciplinary team made up of parents, doctors, pediatricians, educational specialists, psychologists, speech therapists, genetic services, occupational therapists, and nurses, make a complete assessment. Further assessments and evaluations of treatment and management programs should then take place on a regular basis so that the child and adult can maximize skills and lead as fulfilled a life as possible.

Schooling will need to involve a stable, structured program of activities and work that takes into account the person's short attention span and needs for routine and minimal visual and auditory distractions.

People with fragile X often have very good imitation skills and learn best with visual methods of teaching.

Parents and healthcare teams need to work together with the child. Home support services, such as respite care, may be needed by some families in times of stress. Financial and emotional support from caretakers may also be required.

Genetic Counseling for Fragile X

Any family or individual who is concerned that they may be affected or be carriers of fragile X can have the blood test to look for the gene. Genetic counseling can provide information on prenatal diagnosing of a fetus at nine to 10 weeks, advice on termination should the fetus be affected, on fertilization techniques that implant only fertilized eggs whose genetic material is normal.

Genetic counselors can offer ongoing support and information. It can be very difficult coming to terms with any disease. Inherited disorders that can be passed on and stay in the genetic material of many generations can be difficult to cope with psychologically. Fragile X can be present in the permutation form but not always affect the fetus and this also poses difficulties for couples planning a family. Being able to discuss fears and practicalities can be extremely helpful. The genetic counselor can tell affected families what local support groups may be available to them.

What the Future Holds

If someone you love is diagnosed with fragile X, the future their future will depend on many factors such the level of the affected person's functioning, supportive networks, happy home life, educational facilities, good medical and social services. The condition is one that will not go away but the aim should be to maximize skills, live independently and find employment. Some may require supported living and work placements and help throughout their lives.


National Fragile X Foundation

The Fragile X Society UK

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