However, a neurological condition involving intention tremor, ataxia, and cognitive decline has recently been identified among older male carriers of premutation alleles of the FMR1 gene.
This deficit occurred independently of general cognitive impairment but was related to depletion of fragile X mental retardation 1 gene protein product.
The results are also suggestive of factors other than FMRP deficit which may determine some specific cognitive deficits in fragile X pre-mutation carriers.
A neurological syndrome involving progressive action tremor with ataxia, cognitive decline and generalized brain atrophy has been described recently in some adult males with pre-mutation alleles of the fragile X syndrome (FXS) fragile X mental retardation gene (FMR1).
In the fragile X female carriers the degree of cognitive impairment appears to be correlated with activation status of the X chromosome bearing the expanded trinucleotide repeat in the promoter of the FMR1 gene.
Expansion of a polymorphic GCC-repeat at the FRAXE locus has been associated with expression of chromosome fragility at this site and cognitive impairment in some individuals previously testing negative for CGG-repeat expansion in the fragile X mental retardation-1 (FMR1) gene.