Objective: We seek to report the first instance of Spinocerebellar Ataxia Type 17 (SCA17) in a Vietnamese patient with a compound heterozygous mutation in the TATA Binding Protein (TBP) gene, detailing clinical presentation, diagnostic challenges, and genetic variance.

Background: SCA17 is an autosomal dominant neurodegenerative disorder caused by a CAG/CAA repeat expansion in the TBP gene, leading to intranuclear inclusions. It presents variably with progressive ataxia, dementia, and movement abnormalities like chorea and dystonia. While most common in East Asian and Europe, limited genetic testing raises concern for underrepresentation.

Method: Case Report

Results: A 46-year-old female presented with progressive gait, speech, and cognitive changes over seven years. Symptoms began with balance issues and abnormal gait at age 39, followed by slurred speech, mood changes and memory deficits. MRI showed symmetrical cerebellar volume loss and diffuse white matter hyperintensities. She developed repetitive speech, word-finding difficulties, and confabulations four years after the onset of symptoms. Examination showed cerebellar dysarthria and saccadic dysmetria. Her functional history revealed mild changes in decision making. Motor and coordination testing demonstrated bilateral symmetric hyperreflexia in the upper and lower extremities, limb and central ataxia, dystonia, and dysdiadochokinesia. Gait assessment revealed titubation, rigid posture, wide-based stance with reduced stride length, apraxia on turns, and an abnormal pull test. 

The MRI taken at our institution showed extensive cerebellar degeneration out of proportion to other cortical degeneration. An FDG-PET scan showed diminished activity in the cerebellum, and mild diminished uptake in the bilateral frontal lobes, superior parietal region, and bilateral precuneus. Genetic analysis found 41/43 CAG allele repeats in the TBP gene, diagnostic of SCA17. The patient and her family were informed and basic genetic counselling provided. Treatment for SCA17 remains supportive at this time.

Conclusion: This report documents the first case of SCA17 in a Vietnamese patient. The patient is also unique due to being a compound heterozygote and offers further recommendations to differentiate SCAs and diagnose SCA17. It also reiterates the importance of a multidisciplinary approach utilizing clinical presentation, neuropsychological evaluation, and imaging in hereditary ataxias.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/compound-heterozygous-sca17-in-a-vietnamese-patient/