Diagnosing muscular dystrophy

Many different methods can be used to diagnose the various types of muscular dystrophy (MD). The age at which MD is diagnosed will vary depending on when symptoms first start to appear.

Diagnosis will usually involve:

• investigating any symptoms
• discussing any family history of MD
• physical examination
• blood tests 
• a muscle biopsy (when a sample of tissue is removed for testing)

In the first instance, visit your GP if you or your child have any symptoms of MD. If necessary, your GP may refer you to a hospital for further tests.

Investigating symptoms

Your GP will need to know about any symptoms of MD that you or your child have noticed, and when they began to appear. For example, you may be:

• finding it hard to climb the stairs
• unable to play sports as you used to
• finding it hard to lift objects

Identifying when symptoms first appeared and determining which muscles are affected are particularly useful in helping to diagnose different types of MD.

Symptoms in young children

Duchenne MD is the most common type of MD in boys. Symptoms can be present from birth but this is unusual and signs usually appear between 18 months and three years old. You may notice that your child has difficulty walking or climbing stairs, or that they fall down more frequently than other children.

Your child might also find it difficult to stand up from sitting on the floor. They may use what is known as the Gower’s manoeuvre to do this. The Gower’s manoeuvre is where a child stands up by:

• facing the floor
• placing their feet wide apart
• lifting their bottom first
• using their hands to ‘walk up’ their legs (placing their hands first on their knees, then on their thighs)

Visit your GP if you suspect that your child may have MD. Your GP will look at the following when they examine your child.

• The way your child stands.
• The way your child walks. Children with Duchenne MD often have a typical style of walking, which is sometimes described as ‘waddling’. Later on, they may tend to stand and walk on the front part of their foot, with their heels off the ground.
• Whether your child has an exaggerated inward curve of their lower back. The medical term for this is lordosis. It is also sometimes called ‘sway back’.
• Whether your child has an outward or sideways curvature of their spine, known as scoliosis.
• Whether your child’s calves and other leg muscles look large compared with other muscles that may be poorly developed.

Family history

If there is a history of MD in your family it is important to discuss it with your GP. This can help to determine which type of MD you or your child might have.

For example, discussing the family history of limb-girdle MD will help your GP to determine if your type of MD is a recessive or a dominant inherited disorder.  

Blood tests

A sample of blood may be taken from a vein in your or your child’s arm to test it for creatine kinase, a protein usually found in muscle fibres. When muscle fibres are damaged, creatine kinase is released into the blood. The muscle damage caused by MD means that the level of creatine kinase in the blood will be higher than normal.

Muscle biopsy

A muscle biopsy is when a small sample of muscle tissue is taken so it can be examined under a microscope and tested for proteins. The sample will usually be taken from the leg or arm, depending on the type of MD.

Analysing the protein in the muscle can help to determine which gene is causing the MD, and therefore which type of MD you have. For example, people with Duchenne MD and Becker MD have an abnormal amount of the protein dystrophin in their muscles and it is usually an altered size.

Examining the muscle tissue under a microscope can help diagnose limb-girdle MD. Healthy muscle consists of closely packed, evenly-sized fibres. In people with limb-girdle MD, these fibres may be missing, of different sizes or replaced with fat.

Other tests

A number of other tests can be used to find out more about the spread and extent of any muscle damage. This will help your doctor to identify or confirm which type of MD you have. Treatment can then be directed where it is most needed. Some tests are explained below.

• A magnetic resonance imaging (MRI) scan uses a strong magnetic field and radio waves to produce detailed pictures of the inside of your body. This can help to identify the affected muscles, and will also show the extent of any muscle damage.
• A computerised tomography (CT) scan involves taking a series of X-rays to create a detailed image of the inside of your body. This will reveal any muscle damage.
• A chest X-ray can be useful for looking for breathing or heart symptoms. It will show up any abnormal enlargement of the heart, plus any fluid in or around the lungs.
• In an electromyography (EMG) test a needle is inserted into the muscle to measure the electrical activity of the muscles when they are resting and when they contract (shorten). By measuring the muscle’s response, it is possible to see the extent of muscle damage.
• In an electrocardiogram (ECG) electrodes (flat metal discs) are attached to the arms, legs and chest to measure the electrical activity of the heart. This is used to check for an irregular heartbeat and reveal any damage.
• An echocardiogram is an ultrasound scan of the heart using sound waves. It gives a clear picture of the heart muscles and valves so the heart structure and function can be checked.