Mutations in CLC-1, encoded by CLCN1 gene (RefSeq NC_000007.13), lead to either the autosomal dominant form (Thomsen's disease: OMIM 160800) or the recessive form (Becker's disease: OMIM 255700) of myotonia congenita (MC). The gene discussed is CLCN1; the disease is myotonia congenita, autosomal recessive.