Muscular dystrophy

Muscular dystrophy (MD) is the name for a group of inherited genetic muscle conditions. It causes progressive muscle weakness and muscle wasting, because the muscle cells degenerate (deteriorate). This means the condition gets worse over time.

MD often starts in one particular group of muscles and then goes on to affect other muscles in the body.

Muscular dystrophy (MD) is the name for a group of rare, progressive conditions that weaken muscles and cause them to waste away. Muscular Dystrophy UK says there are over 60 of them, affecting 110,000 children and adults in the UK.

Some types of muscular dystrophy are identified by the groups of muscles that are affected first.

The most common types of MD are:

• Duchenne muscular dystrophy (DMD)
• Becker muscular dystrophy
• Facioscapulohumeral muscular dystrophy (FSHD)
• Oculopharyngeal muscular dystrophy (OPMD)
• Myotonic dystrophy
• Limb girdle muscular dystrophies (LGMDs)
• Emery-Dreifuss muscular dystrophy
• Congenital muscular dystrophy (CMD)

Muscular dystrophy (MD) usually develops because a faulty gene has been inherited from one or both parents. It normally runs in families.

MD is caused by mutations (changes) in the genes responsible for healthy muscle structure and function. This leads to muscle weakness and can eventually result in disability.

A gene mutation is like a spelling mistake in the gene code. It can change the protein made in the muscle, and that leads to structural changes and damage in the muscle.

You have 2 copies of every gene (apart from the sex chromosomes), and you get one copy from each parent. If one or both of your parents has the mutated gene that causes MD, it can be passed on to you.

Depending on the type of MD, the condition could be a:

• recessive inherited disorder
• dominant inherited disorder
• sex linked (X-linked) disorder

In rare cases, the genetic mutation can appear as a new event in the family (spontaneous mutation).

If you have recessive inherited MD, you've inherited an altered version of the gene that causes MD from both of your parents. So both copies of your genes are altered.

If you inherit an altered version of the gene from only one parent, you'll be a carrier of the condition. You don't have the condition yourself, but there's a chance you might pass it on to any children you have, if the other parent is also a carrier. The risk of this is very small. If your partner is related to you, the risk is higher.

If both parents carry an altered version of the gene, there's a:

• 1 in 4 chance their child will have MD
• 1 in 2 chance their child won't have MD but will carry the mother's or father's faulty gene
• 1 in 4 chance they'll not have MD and they'll not inherit any mutated genes

If you have a dominant inherited MD, you only need to inherit the altered gene from one parent to be affected. So if you have a child with an unaffected partner, there's still a 1 in 2 chance your child will develop the condition.

The types of MD that are inherited in this way include:

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

Males have one X and one Y chromosome (long threadlike structures of DNA). Females have two X chromosomes.

A sex linked disorder is caused by a mutation in a gene on the X chromosome. Males only have one copy of each gene on the X chromosome, so they'll be affected if one of those genes is mutated.

Females have 2 copies of the X chromosome, so they're less likely to develop an X-linked condition. The healthy copy can usually compensate for (mask) the mutated one. Females can still be affected by X-linked disorders, but the symptoms are likely to be less severe.

Types of MD inherited like this include:

• Duchenne MD
• Becker MD

These conditions are more severe and more common in males.

Sometimes, spontaneous gene mutations can cause MD. This happens when the gene mutates for no apparent reason, changing the way the cells operate. If a person with MD has no family history of the condition, a spontaneous gene mutation might be the cause.

Alternatively, if a child with no family history has MD, the condition may be recessive. There might be gene mutations on both sides of the family, but they haven't affected anyone until a child inherits a copy of the altered gene from both parents.

Doctors use a few different methods to diagnose muscular dystrophy (MD).

Your doctor will ask about your symptoms, or your child's. It helps them to know when the symptoms first appeared and which muscles they affect.

You'll also be asked about your child's development. For example, the doctor will ask what age they started to sit up, stand, crawl and walk. If you have any concerns about your child's overall development, tell your doctor.

Tell your doctor too if anyone in your family has had MD. This might help identify which type of MD you or your child might have. It also helps the doctor to know if anyone in your family has had similar symptoms or has undiagnosed muscle problems.

Your blood sample might be tested for creatine kinase. This is a protein usually found in muscle fibres. When muscle fibres are damaged, creatine kinase is released into the blood. If your muscle damage is caused by some types of MD, you'll likely have a higher level of creatine kinase in the blood than someone without MD.

Your blood sample might also be used for genetic testing, which might help identify the cause of the muscle problems.

You might have a small sample of muscle tissue removed, to be viewed under a microscope and tested for different proteins. Depending on the type of MD you have, the sample might be taken from your leg or arm, either through a small cut (incision) or with a hollow needle.

A muscle biopsy is usually done under local anaesthetic. Children might have the procedure under general anaesthetic. The biopsy can help identify which gene is causing MD, and so which type of MD you have.

There are other tests that can help work out which type of muscular dystrophy (MD) you have.

Other tests might include:

These tests look at the electrical activity in your nerves and muscles, both at rest and when they're in use.

Children may have this test under general anaesthetic.

An MRI scan uses strong magnetic fields to make detailed pictures of the inside of your body. It can help find which muscles are affected and show how far the muscle damage goes.

Sometimes an MRI scan shows a pattern of muscle involvement that tells the doctor straight away which type of MD you have. If that happens, a blood test can be used to confirm the diagnosis and you won't need a muscle biopsy.

A computerised tomography (CT) scan uses X-rays and a computer to build detailed pictures of the inside of your body. It can be used to look for any muscle damage.

A quick, painless X-ray might be used to take pictures of the inside of your body. It looks for any abnormal enlargement of your heart or any fluid around your lungs.

During an electrocardiogram (ECG), electrodes (flat metal discs) are attached to your arms, legs and chest to measure the electrical activity in your heart. The test looks for an irregular heartbeat or any damage in the heart muscle.

An echocardiogram uses ultrasound waves to create a picture of your heart muscles and valves. It checks how well the heart works and what its structure is like.

These are breathing tests, used to assess whether your respiratory muscles have been affected by your condition.

Once your doctor has identified what type of MD you or your child might have, you may be offered genetic testing. Genetic testing can sometimes confirm a diagnosis of a particular type of MD.

It might also be used to find out if you're a carrier of MD, or to confirm a prenatal diagnosis (when a foetus is diagnosed with a condition before birth).

See a doctor if you or your child has:

• muscle weakness
• mobility problems

Muscular dystrophy (MD) has no cure, but there are treatments that can help manage the symptoms.

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

You might slowly lose strength and mobility as your 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 you sleep.

Cough assist machines can help you cough up and clear secretions (phlegm). Using an Ambu bag can help to preserve the strength of your chest wall muscles.

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 come as tablets or as a liquid.

Ataluren (Translarna) is used to treat some children with Duchenne MD who can still walk. It only works for children whose MD is caused by a specific gene mutation. Ataluren can help slow down the progress of muscle weakness. It's prescribed as a sachet of granules, which you mix into a liquid or into food like yoghurt and then eat.

Sometimes MD causes swallowing difficulties (dysphagia), especially as the condition progresses. If food or liquid gets into your lungs, this raises the risk of choking and chest infections. 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 for swallowing problems. This could be a minor procedure called cricopharyngeal myotomy, where one of the muscles in your throat is stretched or cut. Or a small balloon might be inflated in your gullet (oesophagus) to expand and stretch it, which improves swallowing.

If you can't get enough nutrition by swallowing, you might be offered a feeding tube (gastrostomy or PEG). It's placed into your stomach through your abdomen (tummy) during surgery.

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

If you're diagnosed with a type of MD that is likely to affect your heart, your heart function will be closely monitored. You'll have these tests:

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

If your type of MD is likely to cause heart problems, you'll see a cardiologist (heart specialist) for further tests and monitoring. 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. Or you might have an ICD (implantable cardioverter defibrillator) inserted instead.

Bladder problems are common in people with muscle disorders like muscular dystrophy. You might have urinary incontinence, where you pee by accident. This is often caused by weak pelvic floor muscles combined with weak core muscles.

You're more likely to have urinary incontinence if you:

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

Pelvic floor exercise may help. An urgent need to pee can sometimes be helped with medicine.

You might also have bowel problems like:

• chronic constipation
• diarrhoea with little warning
• bowel incontinence

Some people drink less water than is recommended so they don't have to go to the toilet during the day. This can cause dehydration, which makes constipation worse and adds to bowel problems.

Using a gentle laxative like Lactulose regularly during the week may help. Bowel problems can sometimes be helped with medicine too.

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

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

If droopy eyelids 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 is occasionally used to treat weak shoulder muscles. In this operation, the shoulder blades are surgically fixed to the back of the ribs.

If you or your child are offered surgery, you'll be referred to a specialist to discuss the options. This gives you the chance to talk through the risks of any procedure you might have.

Research is ongoing for many types of MD.