Recently, genetic studies in families demonstrating recessively inherited CIP have identified nonsense mutations that result in truncation of the voltage-gated sodium channel type IX α subunit (SCN9A), a 113.5-kb gene comprising 26 exons (MIM# 603415) [Cox et al., 2006; Goldberg et al., 2007; Ahmad et al., 2007; Nilsen et al., 2009]. This evidence concerns the gene SCN9A and hereditary sensory and autonomic neuropathy.