SCN9A and paroxysmal extreme pain disorder: This case report underscores three critical lessons: first, phenotypic heterogeneity in PEPD is far greater than previously recognized, with rare domain IV variants capable of producing devastating, treatment-resistant disease; second, early genetic diagnosis can be lifesaving, averting inappropriate opioid escalation, which is rarely effective in PEPD, enabling cascade testing and family planning, and preserving quality of life; and third, selective Nav1.7 antagonists currently in development may represent prospect of disease-modifying therapy for refractory patients.