Our emphasis is to study the most common nucleotide expansions associated with ataxias. One of these disorders are is associated with premutations in FMR1. Premutations in FMR1 confer an age-dependent risk to develop fragile X-tremor-ataxia syndrome (FXTAS) particularly for male premutation carriers (PMC) from age 50 years. The range of premutations spans between 55-200 CGG repeats in FMR1. More than 200 CGG expansions constitute a full mutation which causes Fragile X syndrome (FXS). FXS is in contrast to FXTAS a non-progressive condition. 20% of female premutation carriers (PMC) develop premature ovarian failure. It is rare for female PMCs to develop FXTAS. Our intention is to characterize a FMR1 cohort and to determine the prevalence of PMC for FMR1, and intermediate alleles for FMR1. Our studies have been approved by the Swedish Ethical Review Authority (Dnr 2016/2503-31/2).