What is Muscular Dystrophy?
The main symptom of muscular dystrophy is muscle weakness. Muscular dystrophy is not a single disease. These diseases are caused by an abnormal or absent protein in muscle cells. This means that the cells and therefore the whole muscle cannot shorten or contract normally. This is experienced as progressive muscle weakness. The type of muscular dystrophy can be diagnosed by examining a muscle biopsy specimen and identifying which muscle protein is either lacking or present in lower than normal quantities.
The commonest types of muscular dystrophy are caused by deficiency or absence of the muscle protein called dystrophin. These types of muscular dystrophy cause progressive muscle weakness. They are called Duchenne and Becker type Muscular Dystrophy. Duchenne is a severe condition; Becker is usually a mild condition.
A good example of muscular dystrophy is Duchenne Muscular Dystrophy. Muscle weakness causes progressive disability from early childhood. This is because the protein dystrophin is missing from muscle cells. In this severe form of muscular dystrophy, all the muscles of the body are affected and the symptoms are muscle weakness that gets worse over time. Mobility is affected first as the skeletal muscles become too weak for walking. As other muscles including the heart muscle and respiratory muscles become weaker, respiratory failure and heart failure due to cardiomyopathy (the term for a heart muscle disorder) develop. There is no cure for muscular dystrophy; management involves controlling the effects of muscle weakness to maintain life and quality of life for as long as possible. Such severe forms of muscular dystrophy are fatal. The emotional effects on a family of diagnosis in early childhood of a progressive severely disabling and eventually fatal disease are significant.
In Becker Muscular Dystrophy the dystrophin protein is present but in less than normal amounts and the affected person may develop some symptoms in childhood but muscle weakness usually becomes a problem only in adulthood.
Muscle proteins other than dystrophin are absent or reduced in the rarer types. Some forms of muscular dystrophy are so rare or so variable in their effects that they are not covered in this guidance – seek medical advice. There are many different types, some of which are quite mild and compatible with a normal life. All of them are inherited and in many a definitive diagnosis can be made on genetic testing or muscle biopsy. The disabling effects of most of these conditions and their prognosis are well described. In this guidance the clinical features and care and mobility considerations of each form of muscular dystrophy will be described separately because the disabling effects and the prognosis of each type are specific. The investigations however, will be described together. It is recommended that the investigations section is used to confirm the diagnosis claimed, if necessary, and then use the appropriate section for clinical features and care and mob. There are some very rare forms of muscular dystrophy which are not included in this guidance because their effects are not well described or very variable – seek medical advice.
