Definition
Fragile X syndrome (FXS) is now the most common known inherited cause of developmental disabilities, but was not discovered until the late 1970s. By 1980 it was found that people showing certain mental and physical characteristics had a chromosomal abnormality caused by a partial break on an X chromosome, called a "fragile site". In 1991 the Fragile X gene was identified within this site.
FXS is named after a site on the long arm of the X chromosome that is elongated and appears partly broken or 'fragile'. The spectrum of Fragile X syndrome ranges from normal development to deve…
