Definition:

Paramyotonia congenita (PMC), which is also known as Eulenburg's disease, is an autosomal dominant inherited disease whose predominant feature is an episodic cold- or exercise-induced muscle myotonia in exposed areas (mainly the face, neck, and hands) that lasts for minutes to hours. The disease may also progress later in life, with stiffness giving way to flaccid paralysis and weakness in exposed or exercised muscles. It is caused by mutations in the sodium channel gene SCN4A.