Myotonia congenita

Congenital myotonia (also myotonia congenita) (Myo- from Greek; muscle, and Tonus from Latin; tension), is a genetic, neuromuscular channelopathy that affects skeletal muscles (muscles used for movement). The disease was first described by Danish/German physician Julius Thomsen in 1876, who himself suffered from the disease. The hallmark of the disease is the failure of initiated contraction to terminate, often referred to as delayed relaxation of the muscles (myotonia) and rigidity. Symptoms include delayed relaxation of the muscles after voluntary contraction (myotonia), and may also include stiffness, hypertrophy (enlargement), transient weakness in some mutations, and cramping.