Several SCN9A sodium channelopathies have been recognized as the cause of rare painful dysautonomic syndromes such as paroxysmal extreme pain disorder and primary erythromelalgia.
Recently, there has been a lot of progress in studying Na(v)1.7 sodium channels (expressed mostly in the sympathetic and nociceptive small-diameter sensory neurons of the dorsal root ganglion) and different mutations affecting the encoding SCN9A gene that leads to channelopathies responsible for some disorders, including primary erythromelalgia.
To describe the clinical phenotype of paroxysmal extreme pain disorder (previously called familial rectal pain syndrome), an autosomal dominant condition recently shown to be a sodium channelopathy involving SCN9A.