Channelopathies: the nondystrophic myotonias and periodic paralyses.

The term channelopathy does not indicate a new group of neuromuscular conditions, but a re-orientation of well- and long-known muscular conditions, the congenital myotonias, and the periodic paralyses. Although, in the past, they have overlapped clinically here and there, both groups were classified differently, as myotonias and as metabolic myopathies, respectively. The discovery of mutations in several ion channels has rewritten nosography of these disorders and procured a new term, the channelopathy-clinical, electrophysiological, and molecular genetic details of which are discussed in this chapter.