Essential tremor-like phenotype in Fragile X carrier women

Tremor is a key feature of the neurodegenerative fragile X-associated tremor ataxia syndrome (FXTAS) and typically affects fragile X gene (FMR1) premutation carriers over the age of 55.

To determine if tremor occurs in FMR1 premutation carriers who do not meet criteria for FXTAS.

Data from two cohorts of premutation carriers (n = 97) and controls (n = 22) were analyzed, and included FXTAS rating scale items such as handwriting, spiral drawing, and finger-to-nose maneuver as rated by a movement disorder neurologist who was blinded to gene status. Premutation carriers who met criteria for FXTAS were excluded. Descriptive, univariate and multivariate methods were used to analyze the differences between the groups.

FXTAS Rating Scale scores were higher in premutation carriers without FXTAS compared to controls (7 ± 5 vs. 4 ± 3, p = 0.002) and remained significantly higher after correcting for age (p = 0.003). Individual tremor items that were significantly worse included finger-to-nose and spiral drawing.

Isolated hand tremor can be seen in FMR1 premutation carriers who do not meet criteria for FXTAS. Additional work needs to be done to determine if these carriers are at higher risk of developing FXTAS in the future or if this is a benign condition. When clinicians are evaluating and counseling FMR1 premutation carriers with tremor, it should be acknowledged that it is not yet know of the individual will develop FXTAS or whether the tremor will remain isolated.