FMR1 and fragile X syndrome: FMR1 PM, although not responsible for FXS, predisposes ~40%–45% of the male [30,31] and ~8%–16% of the female carriers [31,32] to FXTAS, a condition that is characterized by intention tremor, cerebellar gait ataxia, peripheral neuropathy, parkinsonism, memory/cognitive function deficits and other psychological issues [33,34].