FMR1 gene expansion and scans without evidence of dopaminergic deficits in parkinsonism patients.

PURPOSE: To determine if patients with parkinsonism and fragile X mental retardation 1 (FMR1) gene expansions have a striatal dopamine deficit similar to Parkinson disease (PD) patients.

SCOPE: The authors studied three patients with parkinsonism carrying small expansions in the FMR1 gene (41-60 CGG) with [(123)I]β-CIT SPECT imaging. The patients responded to dopaminergic medications, but had preserved dopamine transporter density.

CONCLUSIONS

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).