On Spinocerebellar Ataxia 21 as a Mimicker of Cerebral Palsy.

Objectives: Sporadic variants in ataxia genes may mimic cerebral palsy (CP). Spinocerebellar ataxia 21 (SCA21), a very rare autosomal dominant disease, was discovered to be associated with variants in the transmembrane protein 240 ( Methods: Patients provided oral and written consent. Comprehensive clinical evaluation, neuroimaging studies, review of previous psychometric evaluations, and whole-genome sequencing were applied in both cases. Results: Both patients presented with early-onset ataxia and exhibited mild parkinsonian features. Patient 1 experienced motor and speech delay, autism, and dyslexia, whereas patient 2 experienced dyslexia. Neuroimaging was normal in both cases. In patient 1, the previously reported pathogenic c.509C>T (Pro170Leu) variant in Discussion: Our findings support the notion that SCA21 is a neurodevelopmental syndrome and a mimicker of ataxic CP. Both lack of a family history of ataxia and congenital presentation were reasonable arguments to consider ataxic CP. However, lack of convincing perinatal incidents, progressive symptoms, and the common presence of cerebellar atrophy should alert neurologists about SCA21.