Jain Ashish, Al Khalili Yasir
Conemaugh Memorial Medical Center
Virginia Commonwealth University
Congenital myotonic dystrophy (CMD) is an autosomal dominant disorder caused by a CTG trinucleotide repeat expansion in the DMPK gene on chromosome 19q13.3. It extends well beyond muscle disease; affected individuals may develop cataracts, cardiac conduction abnormalities, insulin resistance, and, in the congenital form, developmental disabilities. Two major forms are recognized: myotonic dystrophy type 1 (DM1), also known as Steinert disease, and myotonic dystrophy type 2 (DM2), which generally has a milder course. As with other trinucleotide repeat expansion disorders, severity correlates with the number of repeats. CMD has an estimated incidence of 1 in 47,619 live births, with neonatal mortality reaching up to 40%. Severe cases follow a distinct “biphasic” natural history in which affected newborns often experience improvement or stabilization of symptoms during infancy, only to develop adult-onset manifestations later in life.
先天性肌强直性营养不良（CMD）是一种常染色体显性遗传病，由位于19号染色体长臂13.3区的DMPK（肌强直性营养不良蛋白激酶）基因中CTG（胞嘧啶-胸腺嘧啶-鸟嘌呤）三核苷酸重复序列扩增引起。DM不仅仅是肌肉营养不良，因为受影响个体还表现出其他器官系统受累，如白内障、心脏传导异常、胰岛素抵抗，先天性形式与发育障碍等有关。文献中描述了两种主要形式。肌强直性营养不良1型（DM1），也称为斯坦纳特病；肌强直性营养不良2型（DM2），它是DM1的一种较轻形式。与任何三核苷酸扩增重复疾病一样，重复次数越多，疾病越严重。CMD的发病率为每47619例活产中有1例，新生儿期死亡率高达40%。严重的CMD表现出独特的“双相”病程；在存活的新生儿中，新生儿症状会改善/稳定，然后在成年后期出现成人发病症状。
