SCA27B in Brazil: frequency, phenotype and genotype-phenotype correlations.

Area of Science:

• Genetics
• Neurology
• Rare Diseases

Background:

• Spinocerebellar Ataxia 27B (SCA27B) is an autosomal dominant ataxia caused by FGF14 gene expansions.
• It is a common subtype in North America and Europe, but its prevalence in Latin America is unknown.

Purpose of the Study:

• To determine the frequency of SCA27B in a Brazilian Spinocerebellar Ataxia (SCA) cohort.
• To characterize the clinical phenotype of SCA27B in this population.

Main Methods:

• Recruited 498 SCA patients from 322 families.
• Collected demographic and clinical data, calculating disease progression rate using the SARA score.
• Utilized PCR-based genetic testing for SCA1, 2, 3, 6, 7, and SCA27B.

Main Results:

• SCA27B was identified in 2.8% of index patients (9/322), making it the fifth most common SCA in Brazil.
• The phenotype included late onset (mean 55.5 years), slow progression (1.0 point/year), and primarily ataxic symptoms.
• Disease progression correlated with age at onset, but not with (GAA)n repeat length.

Conclusions:

• SCA27B is prevalent in Brazil, though less frequent than in Europe/Canada.
• SCA27B should be incorporated into routine diagnostic protocols for SCAs.
• Age at onset may serve as a prognostic marker for SCA27B.