SCN4A and Myotonia: More than 40 mutations have been reported in SCN4A gene, but exons 22 and 24 of SCN4A gene are recognized as hot spots for myothonia,   9  and there is no study investigating on Iranian patients with non-dystrophic myotonia, so the aim of this study was to screen this hotspot exon of SCN4A gene in Iranian patients with non-dystrophic myotonia by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) and sequencing.