SCN9A and erythromelalgia: The fact that we saw selective effects on mechanical pain is interesting and distinct Nav1.7 variants have been linked to particular sensory phenotypes, for instance Nav1.7 variants causing inherited erythromelalgia (IEM) are associated with enhanced thermal pain30 whilst, those causing paroxysmal extreme pain disorder with enhanced mechanical pain4 in the sacral and mandibular regions and painful neuropathy enhanced pressure pain31.