Paroxysmal extreme pain disorder

Paroxysmal extreme pain disorder originally named familial rectal pain syndrome, is a rare disorder whose most notable features are pain in the mandibular, ocular and rectal areas as well as flushing. PEPD often first manifests at the beginning of life, perhaps even in utero, with symptoms persisting throughout life. PEPD symptoms are reminiscent of primary erythromelalgia, as both result in flushing and episodic pain, though pain is typically present in the extremities for primary erythromelalgia. Both of these disorders have recently been shown to be allelic, both caused by mutations in the voltage-gated sodium channel Na_V1.7 encoded by the gene SCN9A. A different mutation in the SCN9A ion channel causes congenital insensitivity to pain.