FMR1 and fragile X syndrome: Since FXTAS is believed to be associated with RNA toxicity, and previous adult patients with FXS and FXTAS features had low bulk (average levels between cells) FMR1 mRNA levels [11–13] similar to those observed in this study, our data suggests that expression of expanded FM alleles may be toxic, independent of high or low bulk mRNA levels, as compared to the control range.