Paramyotonia congenita without paralysis on exposure to cold: A novel mutation in the SCN4A gene (val1293lle)

The autosomal dominantly inherited phenotype of paramyotonia congenita (PC) without paralysis on exposure to cold (MIM 168350) was originally described by De Jong in 1955. This phenotype is clearly different from classical paramyotonia congenita Eulenburg, which has been shown to be a sodium channelopathy resulting from mutations in the gene for the a-subunit of the human skeletal muscle sodium channel gene (SCN4A). From the clinical picture it has always been assumed that PC without paralysis to cold and PC Eulenburg are allelic disorders. In this study we present three German families with PC without cold paralysis, provide evidence that the disorder is linked to the SCN4A gene and report a novel SCN4A mutation (Vall293Ile) segregating in these families.