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Year : 2020  |  Volume : 68  |  Issue : 1  |  Page : 92--93

Autosomal Dominant Spinocerebellar Ataxias: The Subtypes

J M K Murthy 
 Department of Neurology, CARE Institute of Neurosciences, CARE Hospitals, Banjara Hills, Hyderabad, Telangana, India

Correspondence Address:
Dr. J M K Murthy
Department of Neurology, CARE Institute of Neurosciences, CARE Hospitals, Banjara Hills, Hyderabad - 500 034, Telangana

How to cite this article:
Murthy J M. Autosomal Dominant Spinocerebellar Ataxias: The Subtypes.Neurol India 2020;68:92-93

How to cite this URL:
Murthy J M. Autosomal Dominant Spinocerebellar Ataxias: The Subtypes. Neurol India [serial online] 2020 [cited 2020 May 31 ];68:92-93
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Full Text

Adult-onset autosomal spinocerebellar ataxias (SCAs) are progressive disorders in which the cerebellum slowly degenerates, often accompanied by degenerative changes in the brainstem and elsewhere. In this issue of Neurology India, Bhanushali et al. report the analysis of 3-year molecular data of the SCAs referred to one of the private reference laboratory in the country.[1] These data do not reflect the true prevalence of SCAs and the subtypes in the country. However, the data give insight into the prevalence of SCA subtypes in the geographical regions of India. Most of the sampling was from North India and much less from South India. The sample was over-represented by SCA12 and most of it was from North India. Most of the cases of Machado-Joseph disease/SCA3 were from west India. SCA1 and SCA2 subtypes were more in North India.

SCA3 is the common SCA subtype worldwide. In India, SCA2 is the most common SCA subtype.[2],[3],[4] However, in a large series from South India, SCA1 was the common SCA subtype.[5] In 1971, Wadia and Swami described an autosomal dominant cerebellar ataxia, slow saccadic eye movements and peripheral neuropathy.[6] Subsequent studies showed that these patients have pathological expansion at the SCA2 locus.[7]

The most common SCA subtype in this study was SCA12 caused by CAG repeat expansion in the PPP2R2B gene. The length of expanded allele ranges from 51 to 69 CAG triplets.[8],[9] In the current study also, the CAG repeat sizes were in the intermediate zone.[1] SCA12 subtype is found predominantly in Agarwal community in India.[10],[11] Analysis of 20 Indian SCA12 families and ethnically matched normal unrelated individuals revealed one haplotype to be significantly associated with the affected alleles (P = 0.000), clearly indicating the presence of a common founder for SCA12 in the Indian population.[10]

In conclusion, SCA2 is the most common SCA subtype in India. Studies suggest evidence of a common founder for SCA12 in Indian population. There is probably a need for a multicentric study in the country to determine the prevalence of the subtypes of SCAs and also for any regional differences.


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