Do males and females have the same symptoms for Fragile X?

Though Fragile X syndrome (FXS) occurs in both genders, males are more frequently affected than females, and generally with greater severity. 

  • Males (XY) — having only one X chromosome — will develop Fragile X syndrome because they have a mutation of their single (only) X chromosome.
  • Females (XX) — having two X chromosomes — can have the unaffected X reduce the effects of the affected X, which typically leads to no or milder symptoms of Fragile X syndrome. (This is an important distinction, as many females with the full mutation do not consider themselves, nor are they considered by others, to “have” Fragile X Syndrome.)

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