We sought further evidence for the pathogenicity of the variant using muscle velocity recovery cycle (MVRC) analysis, comparing the data for the proband against our previously published data in patients with SCM (n = 9) and PMC (n = 8) (SCN4A mutations)15, and Myotonia Congenita (n = 11, CLCN1 mutations: autosomal dominant n = 5, recessive n = 6, selecting only those who were not on sodium channel inhibitors) and normal controls (NC, n = 26, who were age and sex matched for the myotonia groups)16. Here, SCN4A is linked to Thomsen and Becker disease.