In addition to covering the CACNA1S and SCN4A genes, our panel included five additional genes associated with periodic paralysis, such as RYR1, KCNE3, KCNJ18, KCNJ2 and KCNJ5. Among 21 patients with HypoPP, 15 were classified as having HypoPP-2 with SCN4A variants, and 6 as having HypoPP-1 with CACNA1S variants. This evidence concerns the gene SCN4A and hypokalemic periodic paralysis.