SCN9A and erythromelalgia: Only a minority of patients with Inherited Erythromelalgia possess SCN9A mutations.40 Identification of a genetic cause for erythromelalgia means family genetic counselling and preferential treatment with non-selective sodium channel blockers,41 which is not the standard treatment for other causes of neuropathic pain.42 The family may also access future treatments such as selective sodium channel blockers.43