Paroxysmal extreme pain disorder (PEPD) is an autosomal dominant pain disorder resulting from a set of gain-of-function mutations in SCN9A, the gene encoding Nav1.7, that impair inactivation of Nav1.7. Severe pain in PEPD patients along with flushing is induced by bowel movement or probing of the perianal areas, and is sometimes accompanied by tonic nonepileptic seizures and cardiac deficits. The pain attacks are most severe in the lower part of the body and are often triggered by temperature changes (such as cold winds), eating, and/or emotional upsets (such as crying).
