Family history of cognitive impairment as a diagnostic clue in Fragile X-associated tremor/ataxia syndrome.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder caused by premutation alleles (55-200 CGG repeats) in the FMR1 gene, typically presenting in later adulthood with intention tremor, cerebellar ataxia and cognitive impairment. We report a male patient in his 5th decade presenting with progressive bilateral action tremor initially suggestive of essential tremor. Neurological examination revealed postural and intention tremor with mild dysdiadochokinesia. A family history of early-onset cognitive decline in a first-degree relative prompted brain MRI, which demonstrated bilateral T2 hyperintensities of the middle cerebellar peduncles, suggestive of FXTAS. Subsequent genetic testing confirmed an FMR1 premutation with 115 CGG repeats, establishing the diagnosis of FXTAS. Review of the brother's records revealed progressive cognitive impairment previously attributed to Alzheimer's disease, raising the possibility of unrecognised FXTAS. This case highlights the importance of family history and neuroimaging in distinguishing FXTAS from more common tremor disorders and dementia syndromes.