KCNQ2 and Global developmental delay: In addition, no individual carrying KCNQ2 frameshift variants in homozygosity has ever been described, as minimal KCNQ2 residual activity is probably essential for survival (Lauritano et al., 2019); by contrast, two recent studies reported the occurrence of homozygous frameshift variants in KCNQ3 (each inherited from an asymptomatic parent) in patients with developmental delay and neonatal seizures (Kothur et al., 2018; Lauritano et al., 2019), demonstrating that, homozygous variants in KCNQ3 are compatible with life.