ATP1A3 and alternating hemiplegia of childhood: Approximately 70% of AHC cases are associated with pathogenic variants in ATP1A3, which encodes the catalytic α3 subunit of the neuronal Na+/K+ ATPase protein complex.3–6 Although more than 50 AHC-associated ATP1A3 pathogenic variants have been reported,7 three—D801N, E815K, and G947R—account for more than 65% of ATP1A3-associated AHC cases, with approximate prevalences of 40%, 20%, and 10%, respectively3–6,8–12 (Figure 1A).