['Alternating hemiplegia of childhood and rapid-onset dystonia parkinsonism are two separate movement disorders with different dominant mutations in the same sodium-potassium transporter ATPase subunit gene, ATP1A3.', 'We present a child with topiramate-responsive alternating hemiplegia of childhood who was tested for an ATP1A3 gene mutation.', 'Gene sequencing revealed an identical ATP1A3 mutation as in three typical adult-onset rapid-onset dystonia parkinsonism cases but never previously described in an alternating hemiplegia of childhood case.'] Does identical ATP1A3 mutation cause alternating hemiplegia of childhood and rapid-onset dystonia parkinsonism phenotypes?