Recent human studies have directly linked Nav1.7 to four pain disorders: Primary erythromelalgia (PE), paroxysmal extreme pain disorder (PEPD), Nav1.7-associated congenital insensitivity to pain (CIP) and small fibre neuropathy (Dib-Hajj et al., 2007; Faber et al., 2012). The gene discussed is SCN9A; the disease is peripheral neuropathy.