SCN9A and hereditary sensory and autonomic neuropathy: In humans, loss of function mutations of Nav1.7 lead to congenital insensitivity to pain (CIP), whereas gain of function mutations of Nav1.7 cause inherited erythermalgia (IEM) and proxysmal extreme pain disorder (PEPD) syndromes [4–6], therefore Nav1.7 antagonists should have an application in pain management.