ATP1A3 and Intellectual disability: The purpose of this study was to advance the understanding of phenotypes associated with variants in ATP1A3. Specifically, we reported two cases with symptoms that have not been previously associated with variants in ATP1A3. These symptoms include infantile‐onset of slowly progressive pure cerebellar ataxia and mild to moderate intellectual disability, which have not been previously reported in patients with ATP1A3‐related disorders (Table 1).