Duchenne Muscular Dystrophy

What is Duchenne muscular dystrophy?

Duchenne muscular dystrophy is a genetic condition which affects the muscles, causing muscle weakness. It is a serious condition which starts in early childhood. The muscle weakness is mainly in the 'proximal' muscles, which are those near the trunk of the body, the hips and the shoulders. This means that fine movements, such as those using the hands and fingers, are less affected than movements like walking.

Duchenne muscular dystrophy is a lifelong condition. The muscle weakness is not noticeable at birth, even though the child is born with the gene which causes it. The weakness develops gradually. It usually shows up in early childhood. Symptoms are mild at first, but increase as the child gets older.

The name Duchenne comes from the doctor who first studied this condition.

How common is Duchenne muscular dystrophy?

About 1 in 3,500 boys in the UK get Duchenne muscular dystrophy. There are other types of muscular dystrophy too, which are rarer. There is a separate leaflet called Muscular Dystrophies - An Overview about other types of muscular dystrophy.

What causes Duchenne muscular dystrophy?

The cause is a genetic change which affects the muscles. Muscles contain a protein (chemical) called dystrophin, which is necessary for muscles to function properly. People with Duchenne muscular dystrophy have a shortage of dystrophin in their muscles, and this leads to gradual weakening of the muscles.

The shortage of dystrophin is due to a genetic change, which is why Duchenne muscular dystrophy is a genetic condition. This also means that it can be inherited.

What are genetic conditions?

The body is made of cells, and each cell has a 'control centre' which contains genes. The genes are made of DNA. The purpose of the genes is to tell the cell how to make proteins, which are chemicals needed by the body.

How do genes cause Duchenne muscular dystrophy?

Every person has a large number of genes in their cells. One set of genes is from the father and the other from the mother. The genes have been copied from the parents' cells into the child's cells.

Sometimes during the copying process, the cells make a mistake and one of the genes has a faulty part. In Duchenne muscular dystrophy, the faulty part is in the gene which helps to make the muscle protein called dystrophin. So the muscle cells cannot make dystrophin properly, and the result is muscle weakness.

How is Duchenne muscular dystrophy inherited?

Genes are found on 'chromosomes', rather like houses on a street. The Duchenne muscular dystrophy gene lives on a chromosome called the X chromosome. Boys have only one X chromosome plus a Y chromosome; girls have two X chromosomes. This means that Duchenne muscular dystrophy affects boys rather than girls, because the boys do not have a "spare" X chromosome to compensate for the faulty one. This pattern of inheritance is called 'X linked recessive inheritance'.

Girls have two copies of the X chromosome. So they can 'carry' the Duchenne muscular dystrophy gene without having any problems themselves, because the faulty gene on one X chromosome is balanced by the normal gene on the other X. The Duchenne gene can be passed on from a woman to her child.

Is Duchenne muscular dystrophy always inherited?

No. You might think that each person with a Duchenne gene has inherited this gene from a parent. But in fact, the Duchenne gene can occur in a child without anyone else in the family having the gene. This happens if the faulty gene is made when the child's cells are being formed, without the mother's cells being affected. It means that about half the children with Duchenne muscular dystrophy will not have family members carrying the gene. DNA testing and specialist genetic advice can help to find out whether the Duchenne gene is carried by other members of the family.

What are the symptoms of Duchenne muscular dystrophy?

The symptoms usually start around age 1-3 years. Parents may notice difficulties with:

• Walking, running, jumping and climbing stairs. Walking may look different with a 'waddling' type of walk. The boy may be late in starting to walk (although many children without Duchenne muscular dystrophy also walk late).
• When you pick the child up, you may feel as if he 'slips through your hands', due to looseness of the muscles around the shoulder.
• The calf muscles may look bulky, even though they are not strong.
• As he gets older, the child may use his hands to help him get up, looking as if he is 'climbing up his legs'. This is called 'Gower's sign'.
• Some boys with Duchenne muscular dystrophy also have a learning difficulty. Usually this is not severe. Also, it is not progressive (it does not increase).
• Sometimes, a general delay in development shows up before the muscular dystrophy is diagnosed. If you have a boy whose development is delayed, you may be offered a screening test for Duchenne muscular dystrophy. This would be the 'creatine kinase' blood test (see below). But remember that there are many other causes of developmental delay.

How is Duchenne muscular dystrophy diagnosed?

The diagnosis may be suspected because of the child's symptoms, and by observing his walking and movements. Your doctor may examine the child to check his muscle strength and look for signs of any other condition.

Tests are needed for a definite diagnosis. These are:

• A blood test for creatine kinase: people with Duchenne muscular dystrophy have a very high level of a substance called creatine kinase or 'CK' in the blood (about ten times the normal level or more). If the creatine kinase level is normal, then the child does not have Duchenne muscular dystrophy. But if the level is high, other tests are needed to see whether this is due to Duchenne muscular dystrophy or to some other condition.
  
  
• A muscle biopsy: this involves taking a small sample of a muscle, under local anaesthetic. The sample is examined under a microscope using special techniques to look at the muscle fibres and the dystrophin protein.
  
  
• DNA testing: this is done using a blood sample. The DNA in the blood is tested to look at the dystrophin gene. This test can diagnose most cases of Duchenne muscular dystrophy. However, some cases will not show up on DNA testing, which is why the other tests are also used.

Advice from a genetic specialist

You and your child may be referred to a doctor who specialises in diagnosing genetic conditions (a geneticist). This type of advice is also called genetic counselling.

Genetic advice is useful if you want to know whether anyone else in the family is carrying the Duchenne gene. This information is particularly important if you are considering having more children because you may want to know what is the chance that another child could inherit the Duchenne gene.

If a mother has the Duchenne gene and has another pregnancy, it may be possible to do a prenatal test. This would test whether the unborn baby has the Duchenne gene. A geneticist can give you more information about this option.

What else could it be?

If muscle weakness is the problem, this could also be due to other causes. For example: other types of muscular dystrophy, a 'myopathy' (which is a different type of muscle weakness, which can be temporary or permanent) or a neurological disorder (which affects the nerves controlling the muscles).

If the problem is a young boy with delayed walking or delayed development, there are many other possible reasons for these.

If the query concerns a blood test showing raised creatine kinase, there are various reasons why this can occur, including other types of muscular dystrophy and some muscle injuries. The actual level of the creatine kinase, plus other tests, can help to decide what the cause is. The creatine kinase level in Duchenne muscular dystrophy is always extremely high (ten times normal levels or more).

Usually a diagnosis can be made by taking into account the whole picture - both the pattern of symptoms and the results of the tests. If the results are unclear, it may suggested that you see a doctor who specialises in neuromuscular or genetic conditions.

What is the treatment for Duchenne muscular dystrophy?

There isn't a cure for muscular dystrophy at present. However, there are treatments which can help. This is an outline of the treatments you may be offered:

Information and support

You may need information or support from organisations and parents who have experience of Duchenne muscular dystrophy. See the further information section for suggestions.

Monitoring and general treatment

It is useful to see a specialist team of healthcare staff who have experience treating muscular dystrophy. You may see various doctors, nurses or therapists who each have different expertise. This is because the child may need more than one type of treatment. The aim is to have a teamwork approach, to make sure that everyone works together. Usually the child will be offered regular monitoring, so that if there are problems they can be found and treated as early as possible.

A fairly new treatment for Duchenne muscular dystrophy is corticosteroid treatment, using medicines such as prednisolone or deflazacort. These help to keep the muscles strong. Research has shown that this treatment can slow down the progression of muscle weakness - though it will not cure the problem. Corticosteroids can have side effects, so the treatment needs monitoring. The best time to start corticosteroids needs to be discussed with a specialist, who may monitor the child's muscle strength over a period of time, to help decide when to start this treatment.

Keeping up good general health is important. So you may be advised about things like nutrition, and how much exercise is best for the child.

Treatment in early childhood (preschool age)

At this stage of childhood, Duchenne muscular dystrophy is usually mild. Physiotherapy is useful to help keep the joints and muscles supple. Sometimes night-time splints can help to prevent the ankle joint becoming tight.

Treatments for age 5-9 years

At this age, some support may be needed for the legs and ankles. This is usually night time ankle splints, or sometimes longer braces The ankle joints may become tight with 'contractures' (see below) and an operation can help to release the tight areas around the joint.

9 years onwards

At some time after the age of eight years, the leg muscles become significantly weaker, so that walking gradually gets more difficult, and a wheelchair is needed. The age at which this happens varies from person to person. Often it is around age 9-11 years, although with corticosteroid treatment, some boys can walk for longer.

After the boy starts needing a wheelchair, this is also the time that complications may start, so it is important to monitor the boy's health and to treat any complications early (see below).

Emotions and stress: It isn't always easy being a teenager at the best of times, and having a serious illness means there is more to cope with. Sometimes counselling can be useful, for the child or their family, or both. Support is also available from muscular dystrophy support groups - see further information below.

Practical support may be needed for equipment, care, holidays and breaks. Local health services and care services can help. Certain charities may provide equipment, funding or holidays.

What are the complications of Duchenne muscular dystrophy, and how can they be treated?

Muscle and joint problems

Contractures (tightness around the joints) or scoliosis (curvature of the spine) can occur as a result of muscle weakness. Surgery can be used to treat these.

Chest and breathing problems

During the teenage years, the breathing muscles weaken, causing shallow breathing. This can lead to:

Chest infections, which are harder to clear. Chest infections need treating promptly with antibiotics, and chest physiotherapy helps to clear mucus from the chest. Immunisation with influenza (flu) and pneumococcal vaccines is advised, to help prevent chest infections.

Shallow breathing can cause poor sleep and tiredness. This can be helped in various ways, using physiotherapy and/or equipment. The equipment gives oxygen or provides a higher air pressure to assist breathing. Although this might sound complicated, there are ways of giving breathing support which give less interference with everyday life. For example, it the equipment may only be needed at night, and can use simple devices which fit easily on the mouth or nose to assist breathing.

Later on, as the muscle weakness progresses, more support will be needed for breathing. The treatment of breathing problems has improved over recent years, and this has helped to improve wellbeing and outlook for people with Duchenne muscular dystrophy.

Heart problems

Teenagers and adults with Duchenne muscular dystrophy may develop a heart problem. This is called cardiomyopathy and is due to weakness of the heart muscle. It may cause symptoms such as tiredness, leg swelling, shortness of breath or an irregular heart beat. These symptoms can be helped by medication. The medication seems to work best if started at an early stage, before there are any symptoms. Heart tests such as an ECG (recording of the heart) and 'echo' (ultrasound) can be used to detect cardiomyopathy at this early stage. So people with Duchenne muscular dystrophy should have regular heart checkups with a specialist, starting from early childhood.

Anaesthetics

People with Duchenne muscular dystrophy need extra care if they have a general anaesthetic. Certain anaesthetic medicines can cause a harmful reaction for people who have Duchenne muscular dystrophy. Also, extra care for the chest and breathing is needed. If an anaesthetic is needed, assessment by a senior anaesthetist is important, and extra supervision will be necessary during and after the operation.

Nutrition and digestion

Constipation is a common problem for anyone who is not mobile, including older children who have Duchenne muscular dystrophy. This can be treated with laxatives.

Boys with Duchenne muscular dystrophy are at risk of low bone density, which can lead to osteoporosis. Vitamin D and calcium help to prevent this. These can be obtained from certain foods or from calcium and vitamin D supplements. Vitamin D also comes from sunshine on the skin.

Weight loss or weight gain is sometimes a problem. Excess weight gain can be due to lack of mobility or to corticosteroid treatment. Weight loss can happen if there are a lot of chest infections. Advice from a dietician is useful, and vitamins or supplements can help for someone who is underweight.

What is the outlook for Duchenne muscular dystrophy?

This is a serious condition and it does shorten life. Because the muscle weakness increases gradually over the years, complications eventually develop. The breathing or heart problems usually become more serious for older teenagers or people in their twenties. Without treatment, most people with Duchenne muscular dystrophy do not live beyond their early twenties. Good treatment can make a difference to both wellbeing and the length of life, and may lengthen life up to the person's late twenties.

What about people who carry the gene?

Girls and women who carry the Duchenne gene are usually well and have no symptoms of the condition. Some women with the Duchenne gene do have a slight muscle weakness themselves, but it is mild enough not to affect their everyday lives.

Women carrying the Duchenne gene do have a risk that the condition will be passed on to their children. Usually, there is a 1 in 2 chance that a boy child will have Duchenne muscular dystrophy, and a 1 in 2 chance that a girl child will carry the gene. Prenatal diagnosis during pregnancy may be possible. It is helpful to see a genetic specialist who can give more precise information about your own particular situation.

Rarely, women who carry the Duchenne gene may develop a heart problem, cardiomyopathy - which is explained above in the complications section. For this reason, some doctors recommend that women who have the Duchenne gene have a heart check every five years, starting at around age twenty. Reassuringly, research from the UK found that most women with the Duchenne gene had only very minor changes found on heart checkups. Also, recent research found that there was no difference in life expectancy between women carrying the Duchenne gene and those without the gene.

Might there be any new treatments in future?

There are some ideas, but these are still at the research stage. Possibilities include taking a protein called utrophin, which is similar to the protein dystrophin - the one that is lacking in Duchenne muscular dystrophy. Gene therapy (to replace the faulty part of the gene) is another area of research.

Further help and information

The Muscular Dystrophy Campaign

61 Southwark Street, London SE1 0HL
Helpline: 0800 652 6352 Web: www.muscular-dystrophy.org
This is a UK charity for all muscular dystrophies, neuromuscular disorders and related conditions. It funds research, offers support and advice, and provides information.