In summary, the clinician should consider a FXTAS diagnosis and testing for the Fragile X mental retardation 1 (FMR1) gene premutation if a patient over the age of 50 (1) presents with cerebellar ataxia and/or intention tremor with mild parkinsonism, (2) has the middle cerebellar peduncle (MCP) sign, global cerebellar and cerebral atrophy, and/or subcortical white matter lesions on MRI, or (3) has a family history of fragile X related disorders, intellectual disability, autism, premature ovarian failure and has neurological signs consistent with FXTAS.
The association between FMR1 mRNA level and bradykinesia implicates pathophysiological mechanisms which may link FMR1 mRNA toxicity, dopamine deficiency and parkinsonism in FXTAS.
Therefore, our results indicate that FMR1 GZ allele is potentially associated with parkinsonism in mainland China, and the association is only present in the female patients, but not in the male.
Special emphasis has been placed on the possibility that the modest elevation of 'toxic' FMR1 mRNA in the carriers of grey zone alleles may present an additional risk for some neurodegenerative diseases, such as those associated with parkinsonism, by synergizing with either other susceptibility genes or environmental poisons.
Carriers of fragile X mental retardation 1 (FMR1) repeat expansions in the premutation range (55-200 CGG repeats) often develop a syndrome of kinetic tremor, cerebellar ataxia, and parkinsonism; designated the fragile X-associated tremor ataxia syndrome (FXTAS).
The purpose of this study was to determine the prevalence of fragile X mental retardation 1 repeat expansions in a movement disorder population comprising subjects with all types of tremor, ataxia, and parkinsonism.
Detailed clinical assessment and genetic testing were performed in 14 male carriers of premutation and gray zone FMR1 alleles and in 24 noncarriers identified in a sample of males with parkinsonism.
These results suggest that parkinsonism associated with smaller FMR1 expansions may be related to mechanisms other than pre-synaptic dopaminergic changes and may represent a potential explanation for at least some parkinsonian cases with scans without evidence of dopaminergic deficits (SWEDD).
The results suggest that the FMR1 grey zone alleles, as well as premutation alleles, might contribute to the aetiology of disorders associated with parkinsonism.
The presence of parkinsonism in FXTAS raises the possibility that some individuals who have Parkinson disease are actually carriers of a premutation FMR1 allele.
Fragile X-associated tremor/ataxia syndrome (FXTAS), caused by premutation expansions (55-200 CGG repeats) of the FMR1 gene, shares clinical features with other movement disorders, particularly in the domains of gait ataxia, intention tremor and parkinsonism.
To test the possible association between expanded FMR1 alleles and Parkinson's disease (PD), we determined the size of the FMR1 CGG repeat in 414 male cases of clinically diagnosed parkinsonism, the majority of whom had PD.
To test this hypothesis, we determined the CGG repeat number in FMR1 in 673 individuals with and without parkinsonism and detected 3 premutation carriers (2 patients, 1 control).
Screening of movement disorder patients with other clinical features of FXTAS (e.g., ataxia and parkinsonism) may be more likely to yield expanded FMR1 alleles.