Identical ATP1A3 mutation causes alternating hemiplegia of childhood and rapid-onset dystonia parkinsonism phenotypes

BACKGROUND: 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. PATIENT: We present a child with topiramate-responsive alternating hemiplegia of childhood who was tested for an ATP1A3 gene mutation. RESULTS: 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. CONCLUSION: The discordance of these phenotypes suggests that there are other undiscovered environmental, genetic, or epigenetic factors influencing the development of alternating hemiplegia of childhood or rapid-onset dystonia parkinsonism.