Muscular dystrophy

Muscular dystrophy usually happens because a faulty gene has been passed down from one or both parents, so it tends to run in families.

MD is caused by mutations, or changes, in the genes that are responsible for healthy muscle structure and function. This leads to muscle weakness and, over time, can result in disability.

Think of a gene mutation as a spelling mistake within the gene's DNA code. This mistake can change how a protein is made in the muscle, which in turn causes structural changes and damage to the muscle tissue.

You carry 2 copies of every gene, apart from the sex chromosomes, one inherited from each parent. If one or both of your parents carries the mutated gene that causes MD, it can be passed on to you.

Depending on the type of MD, the condition may be inherited in one of these ways:

• as a recessive disorder
• as a dominant disorder
• as a sex linked, or X-linked, disorder

In rare cases, the gene mutation appears for the first time in a family, as a spontaneous mutation, without being inherited.

If you have recessive inherited MD, you have received an altered version of the gene from both of your parents, so both of your copies are altered.

If you inherit an altered gene from only one parent, you become a carrier of the condition. This means that although you do not have MD yourself, there is a chance you could pass it on to a child, if your partner is also a carrier. This risk is usually very small, though it rises if your partner is a blood relative of yours.

When both parents carry an altered copy of the gene, for each child there is:

• a 1 in 4 chance the child will have MD
• a 1 in 2 chance the child will not have MD but will carry the mother's or father's faulty gene
• a 1 in 4 chance the child will not have MD and will not carry any mutated gene at all

If you have a dominant inherited form of MD, inheriting the altered gene from just one parent is enough to be affected. This means that even with an unaffected partner, there is still a 1 in 2 chance that your child will develop the condition.

Types of MD that are inherited this way include:

• myotonic dystrophy
• facioscapulohumeral MD
• oculopharyngeal MD
• some types of limb girdle MD

Men have one X chromosome and one Y chromosome, the long thread like structures made of DNA that carry our genes, while women have two X chromosomes.

A sex linked disorder is caused by a mutation in a gene sitting on the X chromosome. Because men have only one copy of each gene on the X chromosome, they will be affected if that particular gene is mutated. Women, having two X chromosomes, are less likely to develop an X-linked condition, since the healthy copy of the chromosome can usually cover for the mutated one. Women can still be affected by X-linked disorders, but their symptoms tend to be milder.

Types of MD inherited this way include:

• Duchenne MD
• Becker MD

These forms are more severe and far more common in men.

MD can also arise from a spontaneous gene mutation, where the gene changes for no clear reason and alters the way the body's cells work. If someone with MD has no family history of the condition, a spontaneous mutation may be the cause.

On the other hand, if a child with no known family history develops MD, the cause may still be a recessive form of the condition. Gene mutations may have been quietly present on both sides of the family for generations without affecting anyone, until a child happens to inherit an altered copy from both parents at once.

Read about genetic testing

There are several tests doctors use to work out which type of muscular dystrophy is present.

Your GP will start by asking about the symptoms you or your child have noticed, when they first began, and which muscles seem to be affected. You will also be asked about your child's development, such as the age they started sitting up, standing, crawling and walking, so do mention any concerns you have about their overall growth and development. Let your GP know if MD runs in the family, or if any relative has had similar symptoms or unexplained muscle problems, since this can help point to the exact type of MD involved.

A blood sample may be tested for a protein called creatine kinase, which normally stays inside muscle fibres. When muscle fibres are damaged, this protein leaks into the blood, so people with certain types of MD tend to show higher creatine kinase levels than someone without the condition. The same blood sample can also be used for genetic testing to help pinpoint the underlying cause.

You might also have a small piece of muscle tissue taken, either through a small cut or with a hollow needle, from your leg or arm, so it can be examined under a microscope and tested for specific proteins. This muscle biopsy is usually done under local anaesthetic, though children are often given a general anaesthetic for it. The results can show which gene is responsible, and therefore which type of MD is present.

Other tests

A number of other tests can help narrow down the type of MD, including:

A test that looks at electrical activity in the nerves and muscles, both at rest and during movement. Children may need a general anaesthetic for this test.

An MRI scan, which uses strong magnetic fields to build detailed pictures of the inside of the body. This can show which muscles are affected and how much damage has occurred, and sometimes the pattern seen is distinctive enough to point straight to a particular type of MD, meaning a simple blood test may be enough to confirm the diagnosis without needing a muscle biopsy.

A CT scan, which uses X-rays and a computer to build detailed images of the inside of the body and check for muscle damage.

A quick, painless chest X-ray to look for an enlarged heart or fluid around the lungs.

An ECG, where flat metal discs are placed on the arms, legs and chest to record the heart's electrical activity and check for an irregular heartbeat or damage to the heart muscle.

An echocardiogram, which uses ultrasound waves to picture the heart muscles and valves and check how well the heart is working.

Breathing tests, to see whether the muscles used for breathing have been affected.

Once your healthcare team has a clearer idea of which type of MD is involved, genetic testing may be offered to help confirm the exact diagnosis, check whether someone carries the gene for MD, or confirm a diagnosis made before birth.

Contact your GP practice if you or your child has muscle weakness or problems with mobility.

Treatment for muscular dystrophy

Although there’s no cure for MD, there are treatments that can help to manage the symptoms.

There are many different types of MD and people experience varying symptoms. Your treatment will be tailored to your needs.

You might gradually start to lose strength and mobility as your MD symptoms progress.

Physical problems might be helped with:

• low-impact exercise like swimming
• physiotherapy to work on muscle strength and flexibility
• physical aids like a walking stick, crutches or a wheelchair
• occupational therapy to help maintain independence

If your chest muscles become weak, you might need a machine to help with your breathing. This can be particularly helpful while sleeping.

There are cough assist machines which can help you cough up and remove secretions (phlegm). Using an Ambu bag can help to preserve your chest wall muscle strength.

If you have Duchenne MD, corticosteroid medicine (steroids) can help improve your muscle strength and function. This can slow down the progress of muscle weakness.

Steroids are available in tablet or liquid form.

Read more about steroids and their possible side effects

Ataluren (Translarna) is used to treat some children with Duchenne MD that can still walk. It’s only effective for children with MD with a specific gene mutation.

Ataluren can help slow down the progress of muscle weakness. It’s prescribed as a sachet of granules which can be mixed into liquids or food like yoghurt and eaten.

Sometimes MD can cause swallowing difficulties (dysphagia), especially as the condition progresses. This can increase the risk of choking and chest infections if food or liquid gets into your lungs.

Changing the consistency of your food or learning exercises to improve your swallowing can help prevent choking and chest infections.

You might be offered surgery to treat swallowing problems. This might be a minor procedure where one of the muscles in your throat are stretched or cut in a procedure called cricopharyngeal myotomy. Or a small balloon might be inflated in your gullet (oesophagus) to expand and stretch the gullet and improve swallowing.

If you’re unable to get enough nutrition by swallowing, you might be offered a feeding tube (gastrostomy or PEG). This would be implanted into your stomach through your abdomen (tummy) during surgery.

Your heart muscles, and the muscles you use to breathe, might be affected by MD, depending on which type of MD you have. This can cause life threatening complications.

Your heart function will be closely monitored if you’re diagnosed with a type of MD which is likely to affect your heart.

You’ll have the following tests:

• electrocardiograms (ECGs) to examine your heart rhythm
• echocardiogram
• MRI scan

You’ll see a cardiologist (heart specialist) for further tests and monitoring if the type of MD you have is likely to cause heart problems.

You might be advised to take medicine for your heart problems like ACE inhibitors or beta blockers.

If you have myotonic dystrophy or Emery-Dreifuss MD you might have a pacemaker fitted to help regulate your heartbeat. Alternatively, you might have a ICD (implantable cardioverter defibrillator) inserted.

Bladder problems are common in patients with muscle disorders like muscular dystrophy.

You might experience urinary incontinence, where you pee by accident. This is often caused by weakness of the pelvic floor muscles, combined with weakness of the core muscles.

You’re more likely to experience urinary incontinence if you:

• have poor mobility
• spend a lot of time sitting down

Pelvic floor exercise may be helpful. An urgent need to pee can sometimes be helped with medication.

You might experience bowel problems like:

• chronic constipation
• diarrhoea with little warning
• bowel incontinence

If you tend to drink less water than is recommended to avoid going to the toilet during the day this could cause dehydration. This can make constipation worse and contribute to bowel problems.

Using a gentle laxative like Lactulose regularly during the week may help. can sometimes be helped with medication.

In severe cases of MD, you might be offered surgery to help treat physical problems caused by the condition.

Some types of MD can cause scoliosis. Surgery might be used to correct and to prevent scoliosis from getting worse.

If you have droopy eyelids which are affecting your vision, surgery can help improve this.

Tight joints caused by tendon contractures can be loosened by surgically lengthening or releasing the tendons. This should improve movement.

Scapular fixation, where shoulder blades are surgically fixed to the back of the ribs, is occasionally used to treat weak shoulder muscles.

You’ll be referred to a specialist to discuss surgical options if you or your child are offered surgery. This will allow you to discuss the risks of any procedure you might have.

There is research ongoing for many types of MD. Visit Muscular Dystrophy UK to read about the latest research into treatments for MD.

Muscular Dystrophy UK also provide peer support, support groups, advocacy, practical information and signposting for people living with muscle wasting conditions.

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