Fragile X syndrome

Fragile X syndrome

Fragile X syndrome is a genetic disease and is linked, as its name suggests, to a mutation on the X chromosome. It affects boys and girls, but it is more serious and frequent in boys. Girls may be affected by the syndrome or may simply be carriers of the mutation with hardly any symptoms. It is the first cause of hereditary mental deficiency.


The abnormality on the X chromosome causes a protein to be synthesized abnormally. The amount of protein synthesized (the expression of the gene) determines a greater or lesser range of symptoms. This protein is very important in the first moments of development and continues to be synthesized throughout life. It also determines the functions of other genes, hence the wide range of symptoms that the syndrome presents.


Fragile X syndrome can give a very wide range of symptoms, not all those affected have all the symptoms. There are substantial differences between boys and girls.

Symptoms that may appear in children:

  • Long face, large and displayed ears and joint hyperelasticity
  • Macroorchidism (large testicles): this trait manifests in adolescence
  • squint
  • heart murmur
  • Flat feet
  • Epilepsy (not in all children)
  • Mental retardation
  • Delay in acquisitions and psychomotor
  • Emotional and behavioral disorders
  • Delay in language acquisition
  • Hyperactivity or attention deficit
  • autistic behavior

Symptoms that may appear in girls:

  • Less marked facial features than in children
  • Mental retardation

Children affected by this syndrome have some strengths such as:

  • They are very social and enjoy the company of others.
  • They are very receptive to cooperative work
  • They have a sense of humor
  • Good imitation ability
  • Good visual and long-term memory; have a good sense of direction


The diagnosis is made through a genetic study of DNA and can diagnose boys with the syndrome as well as girls who are carriers of the mutation. It can also be detected prenatally, during pregnancy. Early diagnosis is very important in order to offer the child the best possible medical and educational care.


There is currently no treatment for Fragile X syndrome but in the future gene therapy could give these children a treatment option. Current treatment is based on alleviating symptoms. Medical and educational follow-up is essential.

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