SCN9A mutations have been found in families affected by excruciating pain syndromes including Primary Erythermalgia (PE; OMIM 133020), Paroxysmal Extreme Pain Disorder (PEPD; OMIM 167400), or small-fiber neuropathy (OMIM 133020), as well as by Congenital Insensitivity to Pain (CIP; OMIM 243000), an autosomal recessive disorder in which patients are insensitive to pain caused by fractures, burns, dental extractions, and childbirth. Here, SCN9A is linked to hereditary sensory and autonomic neuropathy.