SCN4A and Thomsen and Becker disease: However, genetic analysis revealed a novel Ile239Thr mutation involving <i>SCN4A</i> gene indicating this case to be a sodium channelopathy.<h4>Conclusion</h4>This case limelight sodium channel myotonia with a novel Ile239Thr mutation in <i>SCN4A</i> gene that phenotypically resembles myotonia congenita but genetically belongs to sodium channelopathy highlighting the poor correlation between genotypes and phenotypes in non-dystrophic myotonia.