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Fragile X Syndrome

  • By: Anne Caroline Wheeler
  • In: Encyclopedia of School Psychology
  • Edited by: Steven W. Lee
  • Subject:School/Educational Psychology (general), School Psychology, Educational Psychology

Fragile X syndrome (FXS), the leading inherited cause of developmental disability, results from an expansion of CGG nucleotide repeats in the fragile X mental retardation gene on the X chromosome. More than 200 repeats are considered a full mutation, which is associated with a reduction of fragile X mental retardation (FMR) protein, known to be essential for normal brain development and function. FXS is associated with mild to moderate cognitive impairment, behavioral difficulties, communication delays, and characteristic physical and behavioral features. Males are affected more severely than females. The estimated prevalence of full-mutation FXS is 1:4000 males and 1:8000 females. During infancy development may appear fairly typical. Moderate to severe delays are observed throughout early to mid childhood and development appears to plateau around ...

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