Queston #8790Note

Paramyotonia congenita is an autosomal dominant disease that presents with cold-induced myotonia due to a mutation in the gene SCN4A. SCN4A codes for a voltage-gated sodium channel. Dysfunction of the gene can also lead to hyperkalemic, hypokalemic, or normokalemic periodic paralysis depending on the type of mutation.

The symptoms of paramyotonia congenita also worsen with activity, which is considered a paradoxical response. The opposite is true for myotoniacongenita, where symptoms typically are worse after a period of rest, and may improve with activity. Myotonia congenita is associated with a CLCN1 gene mutation.