Myotonic myopathies are a group of muscle diseases characterized by a group of affected skeletal muscles that do not relax easily after contraction, diminish or disappear after continuous contraction, and can be aggravated by cold. These include ankylosing myotonic dystrophy, congenital myotonia, and paramyotonia. Etiology and risk factors Most ankylosing myopathies are hereditary diseases. Ankylosing muscular dystrophy is autosomal dominant, and congenital myotonicity is also autosomal inherited. Main types and manifestations 1, ankylosing myotonic dystrophy (atrophic myotonic): the most common, autosomal dominant inherited multisystem disease. It usually develops at the age of 15-25 years. There is a tendency for the offspring to start earlier than the father’s generation. It is more common in males than females. The affected skeletal muscles are tonic and do not relax easily and progressive muscle atrophy. The upper facial muscles, temporalis and sternocleidomastoid muscles are most prominently involved. In a few cases, atrophy of the distal forearm is predominant. The patient has a wasted face, flat forehead lines, drooping eyelids, elevated cheekbones, thick lips, and a slightly open mouth, with a typical axillary head. The neck is long and slender, with an excessive anterior tilt like a goose neck. Almost all have premature baldness and systemic multi-system dysfunction, such as cataract, male testicular atrophy, diabetes mellitus and cardiac arrhythmia, megacolon and cholelithiasis. Myotonicity can be seen when percussion of the piriformis, gastrocnemius and lingual muscles. 2, congenital myotonicity: most are autosomal dominant, a few are recessive. Universal skeletal muscle ankylosis and hypertrophy, the symptoms are aggravated in cold environment, and can be reduced after warmth and repeated activities. Severe cases may cause tonic contraction of the muscles throughout the body after sudden shock and immobilization. The mildest cases may not have any conscious complaints and are only found in genealogical surveys. In individual cases of myotonicity, the symptoms are not reduced but worsened after repeated muscle contractions, which is called paradoxical myotonicity. There are no signs of muscle atrophy or multisystem damage. Percussive muscle ankylosis can be caused by hypertrophy of the peripheral muscles, such as the masseter, quadriceps and gastrocnemius. It is manifested by muscle depression at the percussion site, muscle ball, thumb inversion or inability to separate immediately after palmar pair. Electromyography can be seen as a continuous muscle tonic discharge phenomenon, similar to the sound of a motorcycle start. 3, congenital paramyotonia: a relatively rare genetic disease. The disease starts in early childhood. It is characterized by myotonicity and generalized muscle weakness induced by cold, and the symptoms improve immediately after entering a warm environment. It may gradually improve with age.