“Mimicking” capacity of spinocerebellar ataxia type 3: The details matter

Abstract

We read with interest the article by Dong et al. [ [1] Dong Y. Sun Y.-M. Ni W. Gan S.-R. Wu Z.-Y. Chinese patients with spinocerebellar ataxia type 3 presenting with rare clinical symptoms. J Neurol Sci. 2013; 324: 167-171 Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar ] about spinocerebellar ataxia type 3 (SCA3) patients presenting with rare clinical symptoms. Indeed, as referred by those authors, SCA3 presents one of the most variable phenotypes among spinocerebellar ataxias (SCAs), overlapping not only with clinical presentations of other SCAs, but also with other neurological disorders/syndromes. A clinical diagnosis of SCA3 is suggested in individuals with progressive cerebellar ataxia and pyramidal signs, associated with a complex clinical picture, extending from extrapyramidal signs to peripheral amyotrophy. Besides the three main clinical types (1, 2, and 3), which represent common phenotypes in SCA3, rarer presentations have been assigned to additional clinical types: type 4, associated with parkinsonian features; and type 5, characterized by spastic paraplegia [ [2] Bettencourt C. Lima M. Machado–Joseph Disease: from first descriptions to new perspectives. Orphanet J Rare Dis. 2011; 6: 35 Crossref PubMed Scopus (104) Google Scholar ]. In geographical regions with a high prevalence of SCA3 (e.g., the Azores Islands [ [3] Bettencourt C. Santos C. Kay T. Vasconcelos J. Lima M. Analysis of segregation patterns in Machado–Joseph disease pedigrees. J Hum Genet. 2008; 53: 920-923 Crossref PubMed Scopus (22) Google Scholar ]) its diagnosis is usually suspected. However, when the ethnic/geographic background is unusual for SCA3, the disease segregates in small families or seems sporadic, and/or the phenotype is atypical, the differential diagnosis is tricky and dependent on molecular testing.