Spinocerebellar Ataxia 27: A Review and Characterization of an Evolving Phenotype

BACKGROUND: Spinocerebellar ataxia (SCA) is an uncommon form of progressive cerebellar ataxia with multiple genetic causes and marked variability in phenotypic expression even across patients with identical genetic abnormalities. SCA27 is a recently identified SCA caused by mutations in the Fibroblast Growth Factor 14 gene, with a phenotypic expression that is only beginning to be fully appreciated. We report here a case of a 70-year-old male who presented with slowly worsening tremor and gait instability that began in his early adulthood along with additional features of parkinsonism on examination. Work-up revealed a novel pathogenic mutation in the Fibroblast Growth Factor 14 gene, and symptoms improved with amantadine and levodopa. We also provide a review of the literature in order to better characterize the phenotypic expression of this uncommon condition. METHODS: Case report and review of the literature. RESULTS: Review of the literature revealed a total of 32 previously reported clinical cases of SCA27. Including our case, we found that early-onset tremor (12.1 ± 10.5 years) was present in 95.8%, while gait ataxia tended to present later in life (23.7 ± 16.7 years) and was accompanied by limb ataxia, dysarthria, and nystagmus. Other features of SCA27 that may distinguish it from other SCAs include the potential for episodic ataxia, accompanying psychiatric symptoms, and cognitive impairment. DISCUSSION: Testing for SCA27 should be considered in individuals with ataxia who report tremor as an initial or early symptom, as well as those with additional findings of episodic ataxia, neuropsychiatric symptoms, or parkinsonism.