[Fragile X premutation presenting as postural tremor and ataxia (FXTAS syndrome)]. / Tremblement postural et ataxie révélant une prémutation X fragile ou syndrome FXTAS.

We report a case of FXTAS in a 58-year-old man who presented with postural tremor, mild ataxia and dysexecutive cognitive signs. The syndrome had a slow progressive course. Brain imaging by MRI showed characteristic abnormalities with mild cerebellar atrophy, symmetric high signals in the middle cerebellar peduncles and in the subcortical white matter of cerebral hemispheres. The diagnosis was confirmed by molecular genetics showing by southern blot a 100-120 expansion repeat of the CGG trinucleotide. FXTAS is a recently described syndrome, still unknown by most neurologists and probably rather frequent in men older than 60. We emphasize the value of clinical evaluation and brain imaging by MRI in some patients presenting with non specific motor or cognitive symptoms. A diagnosis of FXTAS may have implications for genetic counselling of female relatives.