What is Fragile X Syndrome?

Fragile X Syndrome is a type of genetic disorder that has symptoms like moderate intellectual disability. Physical characteristics of this syndrome include the narrow and long type of face, ears are large, fingers are flexible and testicles are large. Activity is of hyper type and in 10% of patients will face seizures.fragile-syndrome

The reason for fragile x syndrome is an elongation of the CGG triplet repeat within the fragile X mental retardation 1 (FMR1) gene which is present on the X chromosome. Due to the elongation of a triplet, it leads to such condition when there will be a failure in expressing the fragile X mental retardation protein. This protein is useful in normal neural development. According to the elongated length of this triplet, an allele can be classified as normal, a permutation, and full mutation. With the help of genetic testing, we can easily whether it is fragile X syndrome or not.

  • It is the most common type of mental retardation with a ratio of 1 per 1000 males.
  • The cause of this syndrome is a repeat of nucleotide CGG.
  • All complete mutations are the result of permutation i.e. 56-200 repeats of nucleotides.
  • Through female meiosis expansion of permutation to full mutation occurs.
  • A Severe form of this syndrome depends on the number of nucleotide repeats.


James Purdon Martin and Julia Bell explained a pedigree which describes X linked mental disability. And it is done in 1943. In 1970, Fredrick Hecht gave the term “fragile site”.

Signs & Symptoms:

Main features of this syndrome are:

  • Disability of intellectual type.
  • One or both ears are large in size and they are protruding.
  • Face is long
  • The palate is highly arched.
  • Finger joints are hyperextensible.
  • Thumbs are also hyperextensible.
  • Flat feet and skin are soft.
  • After puberty, testes are large in males.
  • Postpubescent macroorchidism.
  • Muscle tone is low.
  • Single palm crease.


  • It is a type of genetic disorder that can be easily transferred from parents to offspring with the help of DNA.
  • The cause of this syndrome is the mutation of the gene FMR1 (fragile x mental retardation 1) which is present on the X chromosome.
  • It is the result of repetition of trinucleotide.
  • CGG (cytosine, guanine, and guanine) usually repeats itself i.e. is a part of FMR1 DNA. And the repetition is 30 -35 times, rarely it repeats itself 200-800 times.
  • Due to this reason, this gene (FMR1) is not able to make the fragile x mental retardation protein.

Treatment for Fragile X Syndrome:

  • No single or definite treatment is available for Fragile X syndrome.
  • Fragile X Syndrome affected children (who receive a proper education, physical therapy, and medication) they have the best possibility to use their skills and capabilities.
  • Early intervention is very much important.

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