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What causes Fragile X-Associated Tremor and Ataxia Syndrome (FXTAS)?

Because FXTAS occurs only in those who have the premutation on the FMR1 gene, the premutation is related to the condition.

If the premutation was the only cause of FXTAS, then everyone with the premutation would develop FXTAS after age 50. However, it is still not clear why some people with the premutation develop FXTAS while others do not. This topic is an active area of study.