Vydra Darrell G., Rayi Appaji
UT Health San Antonio
Charleston Area Medical Center
Myotonic dystrophy (DM) is considered a subgroup of myopathy and the most common type of muscular dystrophy that begins in adulthood. There are two major forms recognized based on clinical and molecular presentation: Myotonic dystrophy type I (DM1), known as Steinert disease, and myotonic dystrophy type II (DM2), or proximal myotonic myopathy which is a milder variety of DMI. These are progressive, multisystem genetic disorders. Clinical presentation is diverse and can range from asymptomatic electrical myotonia to severe weakness and disability, including cardiac conduction defects, infertility, cataracts, and insulin resistance. A congenital form of DM type 1 is associated with an apparent developmental disability. Myotonia is characterized by impaired relaxation of muscles after voluntary contraction due to repetitive depolarization of the muscle membrane. Myotonia, due to myotonic dystrophy, improves with repeated exercise and is worsened by exposure to cold.
强直性肌营养不良（DM）被认为是肌病的一个亚组，也是成年期开始的最常见的肌营养不良类型。根据临床和分子表现可识别出两种主要形式：I型强直性肌营养不良（DM1），即斯坦纳特病；以及II型强直性肌营养不良（DM2），或称近端强直性肌病，它是DM1的一种较轻类型。这些都是进行性的多系统遗传性疾病。临床表现多样，可从无症状的电肌强直到严重的虚弱和残疾，包括心脏传导缺陷、不孕、白内障和胰岛素抵抗。1型DM的先天性形式与明显的发育障碍有关。肌强直的特征是由于肌膜反复去极化，肌肉在自主收缩后松弛受损。由强直性肌营养不良引起的肌强直，会随着重复运动而改善，而暴露于寒冷环境中会使其恶化。
