SCN9A and erythromelalgia: However, N816 is close to a highly conserved phenylalanine F814, which corresponds to F960 in hNav1.7, which participates in forming the hydrophobic ring lining the cytoplasmic aperture of Nav1.7, along with corresponding residues in the S6 segments of the other domains (Lampert et al., 2008), including the inherited erythromelalgia mutation DIV/F1449 (Dib-Hajj et al., 2005).