Definition:

Inherited erythromelalgia (IEM) is characterized by intense episodic burning pain associated with redness and warmth of the affected extremities and in many instances occurs as an autosomal dominant trait. Symptoms of IEM can start as early as 1 year old (early-onset), or in adults (adult-onset), and both types have been described in families and in sporadic cases. Pharmacotherapy has been largely ineffective, and partial relief of symptoms comes from cooling the affected extremities. Dominantly inherited gain-of-function mutations in SCN9A, the gene encoding Nav1.7, cause IEM.