Muscular Dystrophy is the name given to a group of muscle diseases with certain common characteristics. These characteristics include the development of muscle weakness, wasting and contractures that is usually progressive. The other important characteristic is that the Muscular Dystrophies are all caused by a gene abnormality. This means that Muscular Dystrophies are often inherited. However, for some patients, the gene abnormality was not inherited but arose spontaneously.
肌肉萎缩症是一组有类似特征的肌肉疾病的统称。这些特征包括肌肉衰弱，以及不断恶化的挛缩症状。另一个重要的特征是，这些疾病都是基因异常导致。这意味着肌肉萎缩症通常是遗传疾病。不过，一些病患发病并非跟遗传有关，而是基因发生突变。
Different types of Muscular Dystrophy
There are MANY forms of Muscular Dystrophy. This is a very important point to remember because each form of Muscular Dystrophy has its own characteristics and course. Some are very severe, while others are very mild. Some occur early in life affecting young children, while others start in adults. Different muscles tend to be affected more severely in different Muscular Dystrophies. Some have complications such as involvement of the heart, while others do not. The other important reason to recognize this variety of Muscular Dystrophies is that they are each cause by a different gene abnormality, and therefore, may have different patterns of inheritance. Hence, the risks of acquiring or transmitting the disease are different among the various Muscular Dystrophies. Therefore, for the patient as well as the doctor, it is very important to know and understand exactly WHICH form of Muscular Dystrophy we are concerned with.
肌肉萎缩症有很多类型，每个类型有各自的特征和病发过程，这点非常重要。有的病情非常严重，有的较为轻微。有些病人小时候患病，有些长大后出现症状。不同类型的肌肉萎缩症影响的肌肉部位不一样，严重程度也不一样。有些病患会出现其他并发症，如心脏问题。此外，不同类型的肌肉萎缩症是由不同基因出现异常所引发，因此遗传的途径各有别。有鉴于此，不同类型疾病有着不一样的遗传风险。病患和医生必需知道是患上哪个类型的疾病，才能更好地了解病情。
The Common Types of Muscular Dystrophy
- Duchenne Muscular Dystrophy 杜氏肌肌萎缩症
This is the commonest form of Muscular Dystrophy occurring in children. It usually only affects boys, because the gene is carried on the X sex chromosome (X-linked recessive inheritance). It occurs about 1 out of every 3000 new born male children. In a third of the patients, the abnormal gene arose spontaneously, and is not inherited. Weakness is noticed as the child begins to walk or run. They have difficulty with stairs and fall down easily. Characteristic signs include walking on tiptoe and having large calf muscles. The disease can affect the heart. The weakness progresses so that the boys may lose the ability to walk by the early teens. There is a milder form of Muscular Dystrophy caused by abnormalities in the same gene causing Duchenne Muscular Dystrophy. This milder form is called Becker Muscular Dystrophy. It has the same pattern of inheritance, although it is not as common as Duchenne Muscular Dystrophy. Weakness develops in affected males in early adult life. The disease is also progressive, although the couse is milder. It can also involve the heart.
杜氏肌肌萎缩症是影响孩童的最普遍类型。这类疾病在男童中的比率偏高，因为相关基因存在于X染色体中，是一种隐性遗传病。患上这种疾病的概率是，每3000名新生男童中有一人会患病。三分之一的病患并非遗传发病，而是基因发生突变。患病孩童在走动或跑步时会出现肌肉无力的迹象。他们爬楼梯有困难，也容易跌倒。一些其他特征包括垫脚走路，以及小腿肌肉较大。这类疾病也可导致心脏问题。患病男童肌肉无力的症状会逐步恶化，到了青年初期可能完全无法走路。另一种肌肉萎缩症——贝克型肌肉萎缩症，发生突变的基因与杜氏肌肌萎缩症的一样，但症状较为轻微。它的遗传途径也一样，但不像杜氏肌肌萎缩症那么普遍。患病的男性在成年初期出现肌肉无力症状，并且逐步恶化，但较为轻微。这类疾病也可能影响心脏功能。 - Spinal Muscular Atrophy 脊髓性肌肉萎缩症
This is not a muscle disease in the true sense. However, we are including it in the discussion of Muscular Dystrophy because patients with the disease look very much like patients with Muscular Dystrophy, with problems and treatment needs the are similar. Spinal Muscular Atrophy is actually a disease of the nerve cells that control the muscles and their ability to move and contract. Muscles will only work properly if the nerve cells that control them are working properly. In Spinal Muscular Atrophy, these nerve cells degenerate, resulting in muscle weakness. There are different forms of Spinal Muscular Atrophy, distinguished by the age of onset and the severity of the disease. The most severe form affect infants within a few weeks of life, with severe weakness, loss of muscle tone (floppy), and difficulty feeding and breathing. These infants usually do not survive their first year of life. The milder forms occur in early or later childhood, and these children, although disabled, may and often survive into adulthood. In the more severe forms, recurrent pneumonia can be a serious problem. Like the Muscular Dystrophies, the disease is also caused by a specific gene abnormality. It is inherited in a different way from Duchenne Muscular Dystrophy as the gene is not associated with the sex chromosomes (autosomal recessive inheritance).
这严格上不算是肌肉疾病的一种。不过，这类疾病患者的症状、问题和治疗需要与肌肉萎缩症非常相似，所以我们纳入讨论范围中。脊髓性肌肉萎缩症影响控制肌肉，以及肌肉动作和收缩能力的神经细胞。肌肉的正常运作取决于控制它们的神经细胞。这类病症的导因是神经细胞退化，以致肌肉无力。脊髓性肌肉萎缩症有很多种，它们的发病年龄和严重程度不一样。最严重的病症在婴儿出生几周时出现，肌肉严重无力、肌肉张力松弛，并且有困难喂食和呼吸。这些婴儿通常无法活超过一岁。幼童或孩童较大时的症状较轻微，他们虽然残疾，但通常可长大成人。至于角严重的类别，患者可能经常感染肺炎。与肌肉萎缩症一样，这类疾病是因为某个基因发生突变。它的遗传途径与杜氏肌肌萎缩症不一样，因为基因不存在于X染色体中，不是一种隐性遗传病。 - Myotonic Dystrophy 肌强直型进行性肌肉萎缩症
In Western societies, this is the commonest form of muscular dystrophy among adults. It usually begins in early or mid adult life, although it can start at any age group, including infancy. This disease, in addition to progressive weakness, has several special features. It is associated with a phenomenon called myotonia, in which the muscles have difficulty relaxing after contraction. The patients tend to develop cataracts early. The heart can be involved. The pattern of muscle weakness is also unusual, involving the face, forearm and lower leg muscles. The disease is inherited in a pattern different from both Duchenne Muscular Dystrophy or Spinal Muscular Atrophy (autosomal dominant inheritance).
这是西方国家成年人中最常见的肌肉萎缩症。这类疾病可发生在任何年龄层身上，但通常在成年初或中期发病。除了肌肉逐步无力，患者会出现几个特征，包括患上肌强直症，致使肌肉在收缩后无法松懈。此外，患者也会提早患上白内障，以及出现心脏问题。肌肉无力的症状也较不寻常，影响脸部、前臂和小脚的肌肉。这类疾病的遗传途径不同于杜氏肌肌萎缩症，或脊髓性肌肉萎缩症，后者都属于染色体显性遗传疾病。 - Limb Girdle Muscular Dystrophy 肢带型肌肉失养症
In Limb Girdle Muscular Dystrophy, the muscles of the shoulder and the hip are selectively affected. Limb Girdle Muscular Dystrophy can start in early childhood and look like Duchenne Muscular Dystrophy. Or it can start in adult life. We now know that instead of one disease, there are actually many different diseases, causing what is labelled as Limb Girdle Muscular Dystrophy and caused by different genes. It is important to separate this diagnosis from Duchenne Muscular Dystrophy in children and young adults, as the inheritance and disease course are very different (autosomal recessive or dominant inheritance).
患者的肩膀和臀部的部分肌肉可能受影响。肢带型肌肉失养症的症状与杜氏肌肌萎缩症非常相似，患者一般上在童年初期发病，或可在成年时发病。这类疾病可由多种其他病症引发，并由不同基因突变导致。它的症状也不同于孩童和青年的杜氏肌肌萎缩症，遗传和发病途径也非常不同（染色体隐性或显性遗传病）。 - Facioscapulohumeral Dystrophy 面肩胛肱型肌营养不良症
This form of Muscular Dystrophy is not uncommon. It usually affects adults and can be very variable in its severity. Indeed, there are patients walking around who are so mildly affected that they do not realise that they have this disease. The disease has a characteristic pattern of muscle weakness. The face is weak so that the patients may not be able to whistle or close their eyes in sleep. The shoulder muscles are also affected but again in a selective pattern, involving the upper are muscles. The scapula may stick out at the back. There may also be weakness of the lower leg muscles. Most patients are not seriously disabled, until late in life (autosomal dominant inheritance).
这类疾病相当常见，通常是成年人患病，症状严重程度也不同。有些病患的症状非常轻微，他们可能不知道自己患病，还能够走动。这类患者的肌肉无力症状有一些特征，脸部肌肉疲弱，睡觉时无法闭上眼或吹口哨。他们的肩膀肌肉也受影响，但主要是肌肉上方部位。肩胛骨可能从背部露出，小腿肌肉也可能无力。大部分病患不是严重残疾，直到晚年时可能变得严重（染色体显性遗传病）。 - Congenital Myopathy 先天性肌病
This refers to a large number of different muscle diseases which are caused by gene abnormalities and which are similar to Muscular Dystrophies. These diseases usually start in infancy or early childhood. They may be mild and non-progressive, but can also be severe. Some of the different forms of Congenital Myopathy include: Nemaline Myopathy. Central Core Disease, Myotubular Myopathy. Their pattern of inheritance is very variable (all three forms may occur depending on which specific congenital myopathy).
这指的是由基因突变导致，以及与肌肉萎缩症非常相似的不同肌肉疾病。这些疾病通常在出生时或孩童阶段发病，它们的症状可能较为轻微或不会逐步恶化，但也可能很严重。不同类型的先天性肌病包括杆状体肌病、中央轴空病肌小管病变。它们的遗传途径非常不一样，可能三种疾病同时出现。
By Dr Yee Woon Chee