[Fragile X tremor ataxia syndrome (FXTAS): a new kind of spinocerebelar ataxia associated to fragile X syndrome premutation carriers].

BACKGROUND AND OBJECTIVES: It has been estimated that 1:1233 males and 1:411 females are FMR1 premutated carriers. This gene is responsible for the fragile X syndrome.

PATIENTS AND METHOD: Among 398 fragile X syndrome families, we evaluated 112 premutated carriers older than 50 year.

RESULTS: FXTAS penetrance among fragile X families was 10.7% for female premutated carriers and 29.7% for male premutated carriers. In the general population, it was estimated that 1:4,000 females and 1:5,000 males will develop the FXTAS syndrome.

CONCLUSIONS: Besides the risk for fragile X syndrome, the genetic counseling in premutation carriers should mention the risk for FXTAS. This syndrome should also be taken into account among spinocerebelar ataxia patients with an unknown etiology.