FMR1 and fragile X-associated tremor/ataxia syndrome: For instance, patients who presented both FMR1 mRNA increase and FMRP decrease manifested a symptomatology resembling combined FXS and FXTAS [64], although the mosaicism of methylated and unmethylated FM alleles can also explain the coexistence of FXS and FXTAS-related diagnosis in the same individuals [64,68].