SCN9A and paroxysmal extreme pain disorder: 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.