Spinocerebellar ataxia type 6 in eastern India: Some new observations

Introduction: Spinocerebellar ataxias (SCAs) are hereditary, autosomal dominant progressive neurodegenerative disorders showing clinical and genetic heterogeneity. They are usually manifested clinically in the third to fifth decade of life although there is a wide variability in the age of onset. More than 36 different types of SCAs have been reported so far and about half of them are caused by pathological expansion of the trinucleotide, Cytosine Alanine Guanine (CAG) repeat. The global prevalence of SCA is 0.3-2 per 100,000 population, SCA3 being the commonest variety worldwide, accounting for 20-50 per cent of all cases, though SCA 2 is generally considered as the commonest one in India. However, SCA6 has not been addressed adequately from India though it is common in the eastern Asian countries like, Japan, Korea and Thailand. Objective: The present study was undertaken to identify the prevalence of SCA6 in the city of Kolkata and the eastern part of India. Materials and Methods: 83 consecutive patients were recruited for the study of possible SCAs and their clinical features and genotype were investigated. Results: 6 of the 83 subjects turned out positive for SCA6, constituting therefore, 13.33% of the patient pool. Discussion: SCA6 is prevalent in the eastern part of India, though not as frequent as the other common varieties. Conclusions: Further community based studies are required in order to understand the magnitude of SCA6 in the eastern part, as well as in other regions of India.