Myotonic dystrophy

Myotonic myopathies are a group of muscle disorders characterized by the impaired relaxation of skeletal muscles after voluntary contraction or physical stimulation. This condition is associated with increased muscle excitability upon electrical or mechanical stimulation. Muscle relaxation improves, and symptoms resolve after repeated contractions or electrical stimulation. Myotonia worsens in cold environments. Electromyography reveals continuous high-frequency discharges. This category of diseases includes myotonic dystrophy, congenital myotonia, and paramyotonia congenita.