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Duchenne muscular dystrophy

Published by Bupa's health information team, May 2009.

This factsheet is for parents of children with Duchenne muscular dystrophy, or people who would like information about it.

Duchenne muscular dystrophy is an inherited condition that causes gradual loss of muscle function. It usually only affects boys.

What is Duchenne muscular dystrophy?
Symptoms of Duchenne muscular dystrophy
Causes of Duchenne muscular dystrophy
Diagnosis of Duchenne muscular dystrophy
Treatment of Duchenne muscular dystrophy
Living with Duchenne muscular dystrophy
Questions and answers
Related topics
Further information
Sources

What is Duchenne muscular dystrophy?

Muscular dystrophies are a group of disorders that cause muscle weakness. Duchenne muscular dystrophy is one of the most common types of muscular dystrophy. It causes muscle cells to break down and eventually die, so muscles become progressively weaker.

Duchenne muscular dystrophy usually only affects boys, but it can very rarely affect girls too. About one in 3,500 boys are born with Duchenne muscular dystrophy.

Symptoms of Duchenne muscular dystrophy

The symptoms of Duchenne muscular dystrophy usually start between the ages of one and three. Boys with Duchenne muscular dystrophy may not start walking until later than usual and have difficulty walking. They may be unable to run and jump like other children their age.

As the disease progresses, boys with Duchenne muscular dystrophy get weaker and can't walk as far, or as fast, as other children their age. They may develop a waddling walk, and fall down occasionally.

If a boy has Duchenne muscular dystrophy, he will often work his hands up his legs to help him to stand when he is getting up from the floor. This is called Gower's sign.

Some boys with Duchenne muscular dystrophy have learning difficulties. If your son has severe learning difficulties, he may need to go to a special school.

As boys' muscles weaken, they may also get bigger, especially the calf muscles. But this new muscle tissue won't be strong. As the disease progresses, the heart muscle may grow bigger and weaken, causing problems with the heartbeat. The diaphragm (a band of muscle below the lung) may also weaken, causing problems with breathing.

Eventually, boys with Duchenne muscular dystrophy develop a curved spine (scoliosis). Between the ages of eight and 12, most boys become unable to walk and will need to use a wheelchair.

As boys with Duchenne muscular dystrophy get weaker, they are more likely to get other illnesses such as chest infections and pneumonia. Most boys with Duchenne muscular dystrophy don't live past the age of 20. This is usually because they develop breathing problems or problems with their heart.

Causes of Duchenne muscular dystrophy

Duchenne muscular dystrophy is caused by a faulty gene. This gene usually makes a protein called dystrophin. We need dystrophin to maintain the structure of our muscle cells. Boys with the faulty gene can't produce dystrophin, so their muscle cells break down and eventually die.

The faulty gene is usually passed down to boys from their mother, through a process called X-linked recessive inheritance. However, around three in 10 cases of Duchenne muscular dystrophy are caused by a 'spontaneous mutation'. This means the fault has occurred in the boy's gene itself, rather than being passed down to him from his parents.

Lots of genes make up structures called chromosomes. The faulty gene which causes Duchenne muscular dystrophy is carried on a chromosome called the X chromosome. Females have two X chromosomes, but males only have one. So, if a male has the faulty gene that causes Duchenne muscular dystrophy, he will be born with the disease. But if a female has the faulty gene, she will have another, normal, copy of the same gene on her second X chromosome. The normal gene will compensate for the faulty one, so she won't be affected by Duchenne muscular dystrophy. She will, however, be a carrier of the faulty gene and may pass the disease on if she has a son.

Diagnosis of Duchenne muscular dystrophy

Your doctor will assess your son's physical abilities and may ask to watch him walk, run, jump, walk up stairs and get up from a sitting position on the floor.

If your doctor thinks your son has Duchenne muscular dystrophy, he or she will take a sample of blood from a vein in his arm. The blood sample will be sent to a laboratory and tested for a substance called creatine kinase. All boys with Duchenne muscular dystrophy have a high level of creatine kinase in their blood.

Another sample of your son's blood may be taken so that his DNA (genes) can be examined. The results of this test will show whether he has the faulty dystrophin gene or not.

Your son may also need to have a muscle biopsy. This means a small sample of his muscle will be taken and sent to a laboratory for testing. It can be done in two ways - a needle biopsy or an open biopsy. If your son has needle biopsy, a needle will be inserted through his skin and into his muscle. When it's removed, the needle will bring away a small sample of his muscle tissue. The area will be covered with sterile strips and a plaster afterwards. If your son has as open biopsy, a cut will be made into his skin, so that a sample of muscle can be taken. The cut will be a few centimetres long and will be closed with stitches afterwards.

The sample of muscle will usually be taken from your son's upper arm, shoulder or leg muscle. He will be given either a local or general anaesthetic before the procedure so he won't feel any pain.

The muscle sample will be examined in a laboratory to see how much dystrophin it contains. Boys with Duchenne muscular dystrophy have a very low level of dystrophin in their muscles. Your doctor will usually be able to give you the results of the biopsy around three to four weeks after it was taken.

If a boy has Duchenne muscular dystrophy, it's likely that the faulty gene has been passed on to him from his mother. His mother may need to have creatine kinase and DNA blood tests to see whether or not she is a carrier of the faulty gene.

If you're a carrier of the faulty gene, you will be advised to speak to a genetic counsellor. He or she will be able to work out the risk of any other children you may have in the future being born with Duchenne muscular dystrophy.

Treatment of Duchenne muscular dystrophy

There is no cure for Duchenne muscular dystrophy, but there are ways in which the condition can be managed.

Your son's treatment will involve a team of healthcare professionals, each with a different area of expertise. As your son gets older, he will need to attend a clinic regularly, so that experts in Duchenne muscular dystrophy can treat any problems, particularly with his heart or breathing, early on.

Physical therapy

Exercise is important to keep your son's muscles working and in as good a condition as possible. Stretching and low impact sports, such as swimming, are recommended to keep boys active and flexible.

Physiotherapy will be an important part of your son's treatment. Your doctor should refer your son to a physiotherapist after he has been diagnosed.

Physical aids

Callipers or leg splints are sometimes used to help boys to walk for longer. During the later stages of the disease, your son will become unable to walk and will need to use a wheelchair. He will be given an electric wheelchair with supported seating. You may need to have some special equipment installed in your home to help your son get around in his wheelchair. This will help him to stay mobile for as long as possible.

Medicines

Drugs called steroids are often prescribed to help improve the strength of boys with Duchenne muscular dystrophy. These drugs may slow down the progression of the disease for a while. But taking them for a long time can have side-effects, so it's not always recommended. Steroids are usually only given to boys whose muscles are so weak that it's severely affecting their day-to-day life.

Any respiratory infections your son gets will need to be treated as soon as possible, usually with antibiotics.

Surgery

If your son has severe curving of his spine (scoliosis), he may need to have surgery to correct it. Surgery can make sitting easier and more comfortable for your son, and also help his lungs to work as well as possible.

Sometimes boys need surgery to release very tight and painful muscles. Your son may need to have ankle, knee or hip tendon release. This means that his tendons will be surgically cut so that he can move his joints more.

Living with Duchenne muscular dystrophy

Raising a child with Duchenne muscular dystrophy can have an impact on the whole family. It's often helpful to talk to people in the same position as you. Your paediatrician or GP should be able to help with this. There are also a number of charities and patient groups who can give you advice.