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Table of Contents    
COMMENTARY
Year : 2020  |  Volume : 68  |  Issue : 1  |  Page : 92-93

Autosomal Dominant Spinocerebellar Ataxias: The Subtypes


Department of Neurology, CARE Institute of Neurosciences, CARE Hospitals, Banjara Hills, Hyderabad, Telangana, India

Date of Web Publication28-Feb-2020

Correspondence Address:
Dr. J M K Murthy
Department of Neurology, CARE Institute of Neurosciences, CARE Hospitals, Banjara Hills, Hyderabad - 500 034, Telangana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.279663

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How to cite this article:
Murthy J M. Autosomal Dominant Spinocerebellar Ataxias: The Subtypes. Neurol India 2020;68:92-3

How to cite this URL:
Murthy J M. Autosomal Dominant Spinocerebellar Ataxias: The Subtypes. Neurol India [serial online] 2020 [cited 2020 Apr 7];68:92-3. Available from: http://www.neurologyindia.com/text.asp?2020/68/1/92/279663




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.



 
  References Top

1.
Bhanushali AA, Venkatesan R, Das BR. Spinocerebellar ataxias in India: Threeyear molecular data from a central reference laboratory. Neurol India 2020;68:86-91.  Back to cited text no. 1
  [Full text]  
2.
Sinha KK, Worth PF, Jha DK, Sinha S, Stinton VJ, Davis MB, et al. Autosomal dominant cerebellar ataxia: SCA2 is the most frequent mutation in eastern India. J Neurol Neurosurg Psychiatry 2004;75:448-52.  Back to cited text no. 2
    
3.
Basu P, Chattopadhyay B, Gangopadhaya PK, Mukherjee SC, Sinha KK, Das SK, et al. Analysis of CAG repeats in SCA1, SCA2, SCA3, SCA6, SCA7 and DRPLA loci in spinocerebellar ataxia patients and distribution of CAG repeats at the SCA1, SCA2 and SCA6 loci in nine ethnic populations of eastern India. Hum Genet 2000;106:597-604.  Back to cited text no. 3
    
4.
Saleem Q, Choudhry S, Mukerji M, Bashyam L, Padma MV, Chakravarthy A, et al. Molecular analysis of autosomal dominant hereditary ataxias in the Indian population: High frequency of SCA2 and evidence for a common founder mutation. Hum Genet 2000;106:179-87.  Back to cited text no. 4
    
5.
Krishna N, Mohan S, Yashavantha BS, Rammurthy A, Kiran Kumar HB, Mittal U, et al. SCA 1, SCA 2 and SCA 3/MJD mutations in ataxia syndromes in southern India. Indian J Med Res 2007;126:465-70.  Back to cited text no. 5
[PUBMED]  [Full text]  
6.
Wadia NH, Swami RK. A new form of here do-spinocerebellar degeneration with slow wye movements (nine families). Brain 1971;94:359-74.  Back to cited text no. 6
    
7.
Wadia NH, Pang J, Desai J, Mankodi A, Desai M, Chamberlain S. A clinicogenetic analysis of six Indian spinocerebellar ataxia (SCA2) pedigrees: The significance of slow saccades in diagnosis. Brain 1998;121:2341-55.  Back to cited text no. 7
    
8.
Holmes SE, O'Hearn EE, McInnis MG, Gorelick-Feldman DA, Kleiderlein JJ, Callahan C, et al. Expansion of a novel CAG trinucleotide repeat in the 5' region of PPP2R2B is associated with SCA12. Nat Genet 1999;23:391-2.  Back to cited text no. 8
    
9.
Srivastav AK, Takkar A, Garg A, Faruq M, Clinical behaviour of spinocerebellar ataxia type 12 and intermediate lengthy abnormal CAG repeats in PPP2R2B. Brain 2017;140:27-36.  Back to cited text no. 9
    
10.
Bahl S, Virdi K, Mittal U, Sachdeva MP, Kalla AK, Holmes SE, et al. Evidence of a common founder for SCA12 in the Indian population. Ann Hum Genet 2005;69:528-34.  Back to cited text no. 10
    
11.
Srivastava AK, Choudhry S, Gopinath MS, Roy S, Tripathi M, Brahmachari SK, et al. Molecular and clinical correlation in five Indian families with spinocerebellar ataxia 12. Ann Neurol 2001;50:796-800.  Back to cited text no. 11
    




 

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