Atypical presentation of rapid-onset dystonia-parkinsonism in a toddler with a novel mutation in the ATP1A3 gene.

ATP1A3 gene mutations can result in a spectrum of diseases with diverse neurological manifestations. One such disorder linked to this mutation is rapid-onset dystonia-parkinsonism (RDP), which manifests as dystonia with features of parkinsonism, such as tremors, rigidity, muscle spasms, and bulbar symptoms. Affected patients are typically adolescents or young adults, with symptoms occurring in a rostrocaudal pattern. We report a unique case of a 2-year-old child with an early onset, atypical presentation of RDP. In addition to motor developmental delay, he presented with muscle rigidity and mild asymmetric dystonia of the limbs, with the lower limbs being more affected than the upper limbs. Genetic sequencing of the child revealed a novel heterozygous autosomal dominant mutation of ATP1A3 gene c.173A>G (p. Tyr58Cys). This report highlights that RDP can present with atypical presentations in the paediatric population and adds to existing medical literature on the clinical spectrum of ATP1A3 genetic channelopathy.