- Dinucleotide repeat polymorphisms at the SCN4A locus suggest allelic heterogeneity of hyperkalemic periodic paralysis and paramyotonia congenita. McClatchey, A.I., Trofatter, J., McKenna-Yasek, D., Raskind, W., Bird, T., Pericak-Vance, M., Gilchrist, J., Arahata, K., Radosavljevic, D., Worthen, H.G. Am. J. Hum. Genet. (1992)