However, due to the lack of information on most CLCN1 mutations, on topics such as 1—functional effects on the channel; 2—structural effect on the channel; 3—description or identification of all functional segments of the channel; and 4—the lack of accurate genotype–phenotype correlations in congenital myotonia [2], it has been extremely difficult to relate the available data with the whole MC clinical picture and to establish proper structure–function relationships in the ClC-1 channel, which are vague at this moment. Here, CLCN1 is linked to congenital myotonia.