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Fragile X (FX) is a family of conditions, including Fragile X Syndrome (FXS) and Fragile X Premutation Associated Conditions  (FXPAC).

Fragile X Syndrome (FXS) is an inherited condition whereby the FMR1 gene is switched off, or partially switched off, in X chromosomes. Those with FXS have the ‘full mutation’, whereby those who are carriers have the ‘premutation’.

Fragile X Premutation Associated Conditions  (FXPAC) includes Fragile X-associated Tremor/Ataxia Syndrome (FXTAS), Fragile X Primary Ovarian Insufficiency (FXPOI) and other conditions associated with the Fragile X Premutation.

There is information in English on Fragile X conditions via our colleagues in the U.K. 
For Spanish, please see
For German, please see
For French and a full range of many other languages, please see the website of our Belgium colleagues:
Please also see the list of our member countries' websites for further information 

What is Fragile X?

Fragile X is a family of inherited genetic conditions. The gene which causes Fragile X Syndrome can also impact carriers of the genetic condition.

What is Fragile X Syndrome?

Fragile X Syndrome (FXS) is the most common inherited form of intellectual, developmental and learning disability and autism. The genetic issue that causes FXS lies on a single gene on the X chromosome. If this gene is fully mutated, the gene cannot fulfil its normal function any longer, and the protein it encodes cannot be produced anymore. The lack of the fragile X protein has various effects in different cells of the body, in particular in the brain cells, the neurons. The name of the Fragile X gene is FMR1 = Fragile X Messenger Ribonucleoprotein 1.