Fragile X–associated tremor/ataxia syndrome (FXTAS)

Fragile X–associated tremor/ataxia syndrome (FXTAS) is an “adult onset” neurodegenerative disorder, usually affecting males over 50 years of age. Females comprise only a small part of the FXTAS population, and their symptoms tend to be less severe.

FXTAS affects the neurologic system and progresses at varying rates in different individuals.

All individuals with FXTAS are carriers of what is called a “premutation” of the FMR1 (Fragile X) gene (also known as “premutation carriers”).

In its “full mutation” form the FMR1 gene causes fragile X syndrome (FXS), a different, but genetically related disorder that is present from birth but is often undiagnosed or misdiagnosed for many years.

Female “premutation carriers” can also be affected by Fragile X-associated primary ovarian insufficiency (FXPOI), another of the conditions associated with the change in the FMR1 gene.

What Is FXTAS?

As mentioned, all individuals with FXTAS are premutation carriers of the FMR1 gene (CGG repeats 55-200). The “job” of the FMR1 gene is to make protein (FMRP) that is important in brain development.

Researchers believe that (for unknown reasons) having the premutation leads to the overproduction of FMR1 mRNA (which contains the expanded repeats). They believe that the high levels of mRNA are what cause the signs and symptoms of FXTAS, but more research is needed.

Note: Not all premutation carriers will develop FXTAS, but all individuals with FXTAS have an FMR1 premutation. Researchers are investigating what other factors might contribute to FXTAS in FMR1 premutation carriers.

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