Below are the symptoms of Duchenne muscular dystrophy, the most common form of the disease. The symptoms of Becker muscular dystrophy are similar but tend start in the mid-twenties or later, are milder, and progress more slowly.
- A waddling gait
- Pain and stiffness in the muscles
- Difficulty with running and jumping
- Walking on toes
- Difficulty sitting up or standing
- Learning disabilities, such as developing speech later than usual
- Frequent falls
- Inability to walk
- A shortening of muscles and tendons, further limiting movement
- Breathing problems can become so severe that assisted breathing is necessary
- Curvature of the spine can be caused if muscles are not strong enough to support its structure
- The muscles of the heart can be weakened, leading to cardiac problems
- Difficulty swallowing – this can cause aspiration pneumonia, and a feeding tube is sometimes necessary
Causes of muscular dystrophy
Muscular dystrophy is caused by mutations on the X chromosome. Each version of muscular dystrophy is due to a different set of mutations, but all prevent the body from producing dystrophin. Dystrophin is a protein essential for building and repairing muscles.
Duchenne muscular dystrophy is caused by specific mutations in the gene that encodes the cytoskeletal protein dystrophin. Dystrophin makes up just 0.002 percent of the total proteins in striated muscle, but it is an essential molecule for the general functioning of muscles.
Dystrophin is part of an incredibly complex group of proteins that allow muscles to work correctly. The protein helps anchor various components within muscle cells together and links them all to the sarcolemma – the outer membrane.
If dystrophin is absent or deformed, this process does not work correctly, and disruptions occur in the outer membrane. This weakens the muscles and can also actively damage the muscle cells themselves.
In Duchenne muscular dystrophy, dystrophin is almost totally absent; the less dystrophin that is produced, the worse the symptoms and etiology of the disease. In Becker muscular dystrophy, there is a reduction in the amount or size of the dystrophin protein.
The gene coding for dystrophin is the largest known gene in humans. More than 1,000 mutations in this gene have been identified in Duchenne and Becker muscular dystrophy.7
Diagnosing muscular dystrophy
There are a variety of techniques used to definitively diagnose muscular dystrophy:
The genetic mutations involved in muscular dystrophy are well known and can be used to make a diagnosis.
- Enzyme assay – damaged muscles produce creatine kinase (CK). Elevated levels of CK in the absence of other types of muscle damage could suggest muscular dystrophy.
- Genetic testing – as genetic mutations are known to occur in muscular dystrophy, these changes can be screened for.
- Heart monitoring – electrocardiography and echocardiograms can detect changes in the musculature of the heart. This is especially useful for the diagnosis of myotonic muscular dystrophy.
- Lung monitoring – checking lung function can give additional evidence.
- Electromyography – a needle is placed into the muscle to measure the electrical activity. The results can show signs of muscle disease.
- Biopsy – removing a portion of muscle and examining it under a microscope can show the tell-tale signs of muscular dystrophy.
Treatment for muscular dystrophy
Currently, there is no cure for muscular dystrophy. Medications and various therapies help slow the progression of the disease and keep the patient mobile for the longest possible time.
The two most commonly prescribed drugs for muscular dystrophy are:
- Corticosteroids – although this type of medication can help increase muscle strength and slow progression, their long-term use can weaken bone and increase weight gain
- Heart medications – if the muscular dystrophy impacts the heart, beta blockers and angiotensin-converting enzyme (ACE) inhibitors may be useful
- General exercises – a range of motion and stretching exercises can help combat the inevitable inward movement of the limbs as muscles and tendons shorten. Limbs tend to become fixed in position, and these types of activities can help keep them mobile for longer. Standard low-impact aerobic exercises such as walking and swimming can also help slow the disease’s progression.
- Breathing assistance – as the muscles used for breathing become weaker, it may be necessary to use devices to help improve oxygen delivery through the night. In the most severe cases, a patient may need to use a ventilator to breathe on their behalf.
- Mobility aids – canes, wheelchairs, and walkers.
- Braces – these keep muscles and tendons stretched and help slow their shortening. They also give added support to the user when moving.