To the best of our knowledge, only 17 PEPD disease-causing variants in SCN9A gene are described in the Human Gene Mutation Database (HGMD) 2025.03 (Phenotype ID: 336513054) (Table 3), most of them clustering in domains III–IV of Nav1.7 and impairing fast inactivation, producing persistent sodium currents that hyperexcite nociceptors. The gene discussed is SCN9A; the disease is paroxysmal extreme pain disorder.