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Muscular Dystrophy
What is the cause?
Muscular dystrophy (MD) is a genetic (inherited) condition where slow, progressive, muscle wasting leads to increasing weakness and disability. In Duchenne MD, for example, there's a single genetic fault in the production of a protein in muscle fibres called dystrophin. These abnormal genes may appear for the first time without warning or be passed on from parents.
It's not the muscle stimulating nerves causing the problem unlike other conditions that make muscles weak, but changes in the muscle cells themselves. The mutations bring about changes to the muscle fibres, and interfere with their ability to shorten (contract). As muscle contraction plays an essential part in the functioning of muscles, muscular dystrophy often results in severe disability.
Unable to process the food and oxygen that's normally converted into the energy needed to make the muscle contract, the cells degenerate and are destroyed.
What are the symptoms?
Muscular dystrophy generally causes the following symptoms:
- difficulty walking
- clumsiness
- frequent falls
- difficulty standing
- breathing problems
The range and severity of symptoms varies depending on the type of muscular dystrophy.
For example, in facioscapulohumeral muscular dystrophy the muscles of the shoulders, upper arms and face, are usually affected first.
In Duchenne MD, which only affects boys (with very rare exceptions), the muscles of the pelvis and thighs are affected first. Most boys with the condition experience difficulty in walking between the ages of one and three and are soon unable to run or jump. Some also have learning and/or behavioural difficulties. By the age of eight to 11, they become unable to walk, and by their late teens or 20s the condition is usually life-threatening because of respiratory problems.
All types of MD gradually worsen, but the speed and degree of disability varies. Many people are able to continue managing independently, while others may need full-time help and care.
Who is affected?
Some types of MD, such as Duchenne, affect children, whereas others, such as Becker's, rarely affect people before the age of ten. Some types only affect adults.
Some MDs run in families, but the abnormal gene may also occur without a family history of MDs.
Most of the different types of MD are rare, with Duchenne MD the commonest and most severe. It may be inherited as an X-linked gene, but in 50 per cent of cases it arises as a new mutation. About 100 boys are born with the condition in the UK each year.
A doctor will often diagnose Duchenne and Becker muscular dystrophy by observing the child's posture and the way that he walks.
In extremely rare cases, girls are affected where it is inherited as an autosomal recessive condition. A small number of female carriers of the gene have a mild degree of muscle weakness and are then known as 'manifesting carriers'.
Girls can be affected by some of the other types of muscular dystrophy.
What is the treatment?
There's no cure and, although a great deal can be done to help limit the effects of MDs, there's no way to stop the loss of muscle cells. Intensive research is being carried out around the world to find a cure and
in the future, it may be possible to reverse the effects of myotonic dystrophy.
Existing treatments aim to control symptoms, such as muscle spasm, and enable people to have a good quality of life. They include muscle exercises, because inactivity can worsen the disease, physiotherapy to help maintain muscle strength and flexibility, and physical aids such as braces or wheelchairs to maintain mobility.
As muscular dystrophy is a progressive disease, the condition can affect the individual emotionally, as well as physically. Support groups and organisations help many people come to terms with their situation. Emotional support is important for carers, too.
Genetic counselling, prenatal diagnosis by chorionic villus sampling, and antenatal screening of families with MDs provides an opportunity to prevent these diseases being passed on to children. |
