Channelopathies: episodic disorders of the nervous system.

The field of channelopathies is a newly recognized group of disorders named after the site of their molecular defects--voltage- and ligand-gated ion channels. While voltage-gated ion channel mutants have been recognized for some time in organisms such as Drosophila, the first channelopathy in humans was reported within the last decade. The recognition of this group of disorders began with the definition of the molecular basis of a group of unusual muscle disorders called the periodic paralysis and non-dystrophic myotonias. Interestingly, this group of muscle disorders share some interesting phenotypic features with a number of seemingly disparate human diseases that involve not only skeletal muscle, but also brain and heart. Some similarities that exist among these different disorders include their episodic nature, similarities with regard to factors that precipitate attacks, therapeutic agents which can help to treat or prevent attacks, and in some cases, a degenerative component that arises in addition to the episodic attacks. The study of these diseases, along with the recognition of common clinical and pathophysiological themes among these disorders has led to tremendous growth in our understanding of these diseases and the hope of developing better therapies.