Objective: To investigate association of expanded CAG repeat with autonomic function in SCA2 patients.

Background: SCA2 is a progressive neurodegenerative disorder characterized by gait, limb ataxia and autonomic dysfunction. It is an autosomal dominant disease caused due to expansion of trinucleotide CAG repeats in ATXN2.

Method: A total 137 SCA2 individuals with genetic confirmation were gathered from AIIMS’s Ataxia Clinic. Every patient had a thorough clinical assessment as well as tests for biochemistry, electrophysiology, and radiography. A thorough evaluation of their autonomic function was conducted, which included the following tests: a) deep breathing; b) Valsalva maneuver; c) isometric exercise; d) cold pressor test; and e) postural assessments. If any of the aforementioned testing domains showed abnormalities, autonomic function was deemed abnormal. Their genetic spectrum and autonomic functioning were connected.

Results: Total 137 unrelated SCA2 patients (47 Male and 90 females) had mean (SD) expanded trinucleotide repeats of 41.86(+4.24) with a range of 36-54. Autonomic function parameters were abnormal in 86 (62.77%) with expanded CAG range of 33-54 repeat and normal 51(37.22%) with expanded CAG range 36-48 repeats. In patients with normal Autonomic function, mean (SD), range of age at onset was 28.02(10.86), 16-44 and mean (SD), of CAG repeat is 41.64(3.57). In patients with abnormal Autonomic function, mean (SD), range of age at onset is 34.75 (8.65), 12-52 and mean (SD), of CAG repeat is 40.34(2.50). No significance difference has been observed in these two group.

Conclusion: SCA2, the most prevalent spinocerebellar ataxia in India shows great clinico-genetic heterogeneity. Our study shows that number of Trinucleotide repeats (TNR) may not be causal for abnormal autonomic function in SCA2 patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/association-of-expanded-cag-repeat-with-autonomic-function-in-spinocerebellar-ataxia-type-2-sca-2/