The link between an Nav1.7 mutation and erythromelalgia
The landmark paper discussed in this chapter is ‘Gain-of-function mutation in Nav1.7 in familial erythromelalgia induces bursting of sensory neurons’, published by Dib-Hajj et al. in 2005. The voltage-dependent sodium channels Nav1.7, Nav1.8, and Nav1.9 have a restricted pattern of expression in sensory neurons in the periphery and are concentrated in small nociceptive neurons of the dorsal root ganglion, the trigeminal ganglion, and the nodose ganglion. In this paper, Dib-Hajj and colleagues studied a family with erythromelalgia (Weir Mitchell disease), an autosomal-dominant, inherited pain disorder in which burning pain in the extremities can be triggered by warming of the skin or moderate exertion. By identifying a novel mutation in SCN9A, which encodes Nav1.7, they established the critical role of this specific ion channel in this patient population. These findings represent an important first step towards developing isoform-specific channel blockers for the treatment of an inherited chronic pain condition.