The neonatal NaV1.5 variant differs from the adult isoform by 7 amino acids in the S3 and the S3/S4 linker from domain I, and is also found in neuroblastoma (Ou et al., 2005), where another splice variant of NaV1.5 lacking the full exon 18 (NaV1.5-Δ18) has been shown to generate a functional sodium channel, even though this exon encodes 54 amino acids in the intracellular loop between domains II and III (Ou et al., 2005). The gene discussed is SCN5A; the disease is neuroblastoma.