The Phenotypic Spectrum of Spinocerebellar Ataxia Type 19 in a Series of Latin American Patients.

Spinocerebellar ataxia 19 (SCA19) represents a rare autosomal dominant genetic disorder resulting in progressive ataxia and cerebellar atrophy. SCA19 is caused by variants in the KCND3 gene, which encodes a voltage-gated potassium channel subunit essential for cerebellar Purkinje cell function. We describe six cases from Chile and Mexico, representing the largest report on SCA19 in Latin America. These cases encompass a range of clinical presentations, highlighting the phenotypic variability within SCA19 from an early-onset, severe disease to a late-onset, slowly progressive condition with normal lifespan. While some patients present with pure ataxia, others also show cognitive impairment, dystonia, and other neurological symptoms. The correlations between specific KCND3 variants and phenotypic outcomes are complex and warrant further investigation. As the genomic landscape of spinocerebellar ataxias evolves, comprehensive genetic testing is becoming pivotal in improving diagnostic accuracy. This study contributes to a better understanding of the clinical spectrum of SCA19, laying the groundwork for further genotype-phenotype correlations and functional studies to elucidate the underlying pathophysiology.