In our Family B, both the proband and her father were heterozygous for a 41-repeat expansion in TBP. Repeat expansions of 41–45 in TBP have been described as intermediate penetrant alleles associated with SCA17 [23,24]; however, the pathogenicity of the 41-repeat expansion allele has been questioned since it is present at a minor allele frequency of 0.5–0.7% in control populations [25,26] and has been found in many asymptomatic individuals [27]. The gene discussed is TBP; the disease is spinocerebellar ataxia type 17.