FMR1 and fragile X-associated tremor/ataxia syndrome: All the above data further illuminates the still unsolved problem of a diversity of clinical manifestations in PM carriers ranging from normality to the most severe involvement in the form of FXTAS, which must clearly depend on the final effect of interplay, in individual carriers, between cellular stresses including toxicity of FMR1 mRNA, linked with the chain of stressful biochemical changes, and cellular stress responses.