Spinocerebellar Ataxia Type 23 (SCA23): A Rare Cause of SCA in the Americas.

Spinocerebellar ataxia type 23 (SCA23) is a rare autosomal dominant hereditary ataxia caused by a pathogenic variant in the PDYN gene. It usually presents in adulthood, with a mean age of onset around 43 ± 15 years (reported range: 10–73 years), and progresses slowly with cerebellar symptoms. We report a case of a Brazilian 25-year-old female patient whose symptoms began at 19 years of age, characterized by progressive dysarthria, tremor, dysphagia, and gait disturbance. She had no relatives with similar symptoms. The initial genetic ataxia panel, which included the most prevalent hereditary ataxia genes, was negative. Subsequent next-generation sequencing identified a pathogenic variant in the PDYN gene, confirming the diagnosis of SCA23. Brain MRI demonstrated significant cerebellar atrophy. The patient was referred to a multidisciplinary rehabilitation group with emphasis on functional rehabilitation of gait and dysphagia. This case is notable for the rarity of SCA23 in the Americas, the relatively young age at onset compared with the reported mean age in the literature, while still remaining within the previously described age range, and the absence of a family history of ataxia or other neurological symptoms, despite SCA23 having an autosomal dominant inheritance pattern.