 Finally, Nav1.7 expressed in sympathetic neurons is critical for normal behavioural responses to neuropathic pain assays.Mutation in Nav1.7 may result in primary erythromelalgia (PE), an autosomal dominant, inherited disorder which is characterized by attacks or episodes of symmetrical burning pain of the feet, lower legs, and sometimes hands, elevated skin temperature of affected areas, and reddened extremities.The mutation causes excessive channel activity which suggests that Nav1.7 sets the gain on pain signaling in humans.