Individuals with heterozygous loss-of-function ATP1A3/ Na/K ATPase α3 variants display developmental delay, postnatal microcephaly, spasticity, axial hypotonia, and learning deficits (Holm et al, 2016; Holm and Lykke-Hartmann, 2016; Smith et al, 2021; Sweney et al, 2015). This evidence concerns the gene ATP1A3 and microcephaly.