ClinVar

In a patient with familial hyperkalemic periodic paralysis (HYPP; 170500), Rojas et al. (1991) identified a heterozygous A-to-G transition in the SCN4A gene, resulting in a met-to-val substitution in a highly conserved region of the alpha subunit, predicted to be in S6 of transmembrane domain IV. The same change was found as a new mutation in a sporadic case. Rojas (1992) stated that the transition occurred at nucleotide 4774 and changed met to val at residue 1592 (M1592V). Heine et al. (1993) found the M1592V mutation in 6 families with a myotonic, nondystrophic form of HYPP.

Kelly et al. (1997) described a large kindred in which affected members were phenotypically heterogeneous with episodic potassium-sensitive paralysis as well as stiffness and weakness induced by exercise and cold, suggesting a combined paramyotonia congenita (PMC; 168300)/HYPP phenotype. Affected members had a heterozygous M1592V mutation, and the authors commented on the phenotypic variation associated with this mutation.