Thomsen Disease

Thomsen Disease

Congenital myotonia (also myotonia congenita) is a genetic, neuromuscular channelopathy that affects skeletal muscles (muscles used for movement). It is congenital, meaning that it is present from birth. Amongst other problems, it causes delayed relaxation of the muscles (myotonia) and rigidity. The disorder is caused by mutations in the part of an ion channel gene responsible for shutting off electrical excitation in the muscles, causing muscle fiber membranes to have an unusually exaggerated response to stimulation (hyperexcitability). Symptoms include delayed relaxation of the muscles after voluntary contraction (myotonia), and may also include stiffness, hypertrophy (enlargement), sluggishness of the muscles, transient weakness in some mutations, pain, and cramping. The disorder is caused by a genetic mutation involving the chloride channel of the muscles. In addition to humans, it is also seen in some goats, canines, cats and one breed of pony.