Objective: We report the spinocerebellar ataxia 13 (SCA13) patient who demonstrated childhood-onset pure cerebellar ataxia.

Background: SCA13 is a rare cause of autosomal-dominant cerebellar ataxia, which is caused by a heterozygous mutation in the KCNC3 gene, which results in voltage-gated potassium channel dysfunction. SCA 13 should be considered in individuals with the following age-related phenotypes. In cases of childhood-onset SCA13, the patient is characterized by progressive ataxia with occasional cognitive decline and/or seizures.

Method: A 17-year-old woman visited our clinic with progressive tremor and dysarthria started in her early teens. Developmental delays or seizures were denied. Her mother also exhibited the tremor and gait unsteadiness. Neurological examination revealed cerebellar-type dysarthria, hypermetric saccades, and limb ataxia. The Scale for the Assessment and Rating of Ataxia (SARA) score was 2.5. Other neurological abnormalities, such as pyramidal or extrapyramidal signs or sensory loss, were not observed. The deep tendon reflex was hyporeflexia on the right side. Cognition was grossly intact. She could walk independently and perform most of the activities in daily life.

Results: Brain magnetic resonance imaging (MRI) demonstrated diffuse cerebellar atrophy; the brainstem and middle cerebellar peduncles were relatively preserved. Genetic tests for SCA1, SCA2, SCA3, SCA6, SCA7, SCA8, SCA17, and dentatorubral-pallidoluysian atrophy were normal. Next-generation sequencing using an ataxia panel identified a pathogenic variant, c.1268G>A (p.Arg423His) in the KCNC3 gene.

Conclusion: Next-generation sequencing using an ataxia panel identified a pathogenic variant, c.1268G>A (p.Arg423His) in the KCNC3 gene. 3-years later, Her symptoms slightly got worse and the SARA score was 5. The brain MRI also showed mildly progressive cerebellar atrophy than the previous study.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/case-report-of-spinocerebellar-ataxia-13-presenting-with-pure-cerebellar-ataxia/