Intrafamilial variability in fragile X-associated tremor/ataxia syndrome

Fragile X–associated tremor/ataxia syndrome (FXTAS) is a progressive adult‐onset tremor/ataxia syndrome caused by premutations in the FMR1 gene. In cranial MRI, the most characteristic findings are bilateral T2 hyperintense lesions within the middle cerebellar peduncles. Here we present a sibpair of two affected brothers presenting with very different symptoms (typical FXTAS versus essential tremor‐like), disease progression, and MRI findings, illustrating broad intrafamilial variability of FXTAS. Also, their family history suggests further evidence of possible manifestation of FXTAS in women. © 2005 Movement Disorder Society