FMR1 and Cognitive impairment: Since the realization that FMR1 mRNA was upregulated in blood samples bearing the PM range compared to controls, concomitant with a reduction in the number of FMRP+ lymphocytes [60], and fueled by early indications of an association of these changes with cognitive deficits in certain PM carriers [88], it has been usual to implement the examination of mRNA and/or protein levels besides the number of CGG repeats as potential correlates of the development of specific symptoms and the severity of the general pathological phenotype.