A newly approved drug for a rare group of diseases Dichlorphenamide for periodic paralysis

The periodic paralyses constitute a group of autosomal dominantly inherited myopathies characterized by acute and reversible attacks of muscle weakness associated with changes in serum potassium levels. In addition to paralytic episodes, patients may develop persistent and progressive muscle weakness. Over the past 2 decades, the periodic paralyses have been models for basic and translational research because they are the foundation for the development of the concept of channelopathies.(1-3) Before the discovery of disease-causing mutations in genes coding for the voltage-gated sodium, calcium, potassium, and chloride channels, disruption of such important proteins that have a central role in the genesis and propagation of action potentials seemed incompatible with life.(4,5) Investigators have subsequently found causal mutations in genes encoding ion channels in epilepsies, ataxias, and cardiac arrhythmias.(6) Periodic paralysis and related muscle ion channel disorders were also among the first diseases for which dissecting the action of a drug on its target directly influenced targeted treatment.(7) Finally, the periodic paralyses were among the first disorders in which understanding of the physiologic basis of symptoms enhanced diagnostic accuracy by electrodiagnostic testing and DNA sequencing.(8)