SCN9A and erythromelalgia: Mutations in the Nav1.7 encoding gene Scn9a are associated with various pain disorders, such as inherited erythromelalgia, paroxysmal extreme pain disorder and small-fiber neuropathy.70 Inhibiting Nav1.7 functions effectively mitigates neuropathic pain and stimulates the production of endogenous opioids.71 The role of Nav1.7 varies with different types of pain.