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Keywords:

  • SCA3;
  • Machado-Joseph disease;
  • Parkinson's disease;
  • ataxia;
  • epidemiology;
  • genetics

Abstract

We describe several families of African origin with SCA3/Machado-Joseph disease gene expansions. In these cases, the phenotype ranges from ataxia with parkinsonian signs to a syndrome clinically almost indistinguishable from idiopathic, L-dopa–responsive Parkinson's disease. In contrast, these parkinsonian phenotypes are rare in those of European descent. Haplotype analysis shows that these African families do not share a common founder, thus a cis-acting element in the promoter is unlikely to be responsible these unusual presentations. We suggest that trans-acting factors are responsible for the variable phenotype and discuss the implications of diseases showing racially different expressivities. © 2002 Movement Disorder Society