CLCN1 and Dyggve-Melchior-Clausen disease: MC caused by CLCN1 mutations that encode the voltage-gated chloride channel (ClC-1) in the skeletal muscle is classified into the autosomal dominant (AD) Thomsen's myotonia congenita (DMC) and the autosomal recessive (AR) Becker's myotonia congenita (RMC) according to the mode of inheritance.