SCN9A and Erythema: This is best illustrated by comparing the NaV1.9-V1184A-related disease with a primary erythromelalgia phenotype caused by the homologous mutation p.V1316A in NaV1.7 (ref. 10): p.V1316A in NaV1.7 causes warmth-aggravated severe burning pain in the body extremities, erythema in the affected body regions, and pain relief on cooling.