Duchenne muscular dystrophy (DMD)
Duchenne muscular dystrophy (DMD)
Overview
Duchenne muscular dystrophy (DMD) is a muscle wasting condition that causes progressive muscle weakness. It usually only affects males.
It’s caused by a lack of a protein called dystrophin. This causes muscle fibres to break down. They’re replaced by fibrous or fatty tissues that cause the muscle to gradually weaken.
DMD is a severe type of MD and often shortens life expectancy. Most people with DMD will reach adulthood. They are, however, more likely to die from heart or respiratory failure before or during their 30’s.
Common Symptoms
⚠️ This symptom list is for educational purposes. Having these symptoms does not mean you have this condition. See a doctor for proper diagnosis.
Medicines Commonly Used
⚠️ These medicines are commonly used for confirmed diagnoses of this condition. This is NOT a recommendation or prescription. Treatment must be determined by your doctor.
No medicines have been linked to this condition yet.
Causes
Causes of DMD
DMD is a type of sex linked (X-linked) muscular dystrophy.
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.
As males only have one copy of the gene on the X chromosome, they’ll be affected if one of those genes is mutated.
Because females have 2 copies of the X chromosome, they’re less likely to develop an X-linked condition. This is because the healthy copy of the chromosome can usually compensate for (mask) the mutated version. This means that although females can still be affected by X-linked disorders, the symptoms are likely to be less severe.
Diagnosis
Doctors use several methods to diagnose muscular dystrophy. Diagnosis might involve looking at your symptoms and family history, a physical exam, blood tests, electrical tests on the nerves and muscles, and sometimes a muscle biopsy, where a small sample of tissue is removed for testing. A blood test is normally enough to confirm a diagnosis of DMD.
Treatment
Treatment cannot cure Duchenne muscular dystrophy, but there is a great deal that can be done to ease its symptoms and help your child live as fully and comfortably as possible.
If your child has Duchenne MD, corticosteroid medicine (commonly called steroids) can help improve muscle strength and function. This can slow down how quickly muscle weakness progresses. Steroids are available as tablets or as a liquid. Ask your doctor about steroids and their possible side effects so you know what to expect.
Ataluren (brand name Translarna) is given to some children with Duchenne MD who can still walk. It only works for children who have a specific gene mutation, so your doctor will need to confirm this before prescribing it. Ataluren can also help slow the progress of muscle weakness. It comes as a sachet of granules that can be mixed into liquid or soft food, such as yoghurt, and eaten.
By around age 11, a child with DMD may start needing a wheelchair. At first this might only be for covering longer distances, but over time it usually becomes needed all day. Around this stage, your child may also start finding it hard to lift their arms above shoulder height. Splints or a spinal brace can help support posture and make movement easier.
Duchenne MD can also lead to scoliosis, a curving of the spine. Surgery may be used to correct it or to stop it from getting worse.
Many people with DMD go on to develop a heart condition called dilated cardiomyopathy. The same faulty gene that affects the muscles also affects the heart, causing its chambers to enlarge and its walls to thin. Because of this, regular electrocardiograms (ECGs) will be done to check heart rhythm, along with an echocardiogram, and sometimes an MRI scan to look more closely for heart problems. Your child will also be seen regularly by a cardiologist (a heart specialist) for further tests and follow up. The cardiologist may prescribe medication to support heart function, and in some cases an ICD (implantable cardioverter defibrillator) may be fitted to help the heart work properly.
Breathing difficulties are common as the condition progresses, and many children need a machine to help them breathe at night, and sometimes during the day as well. In older children, a cough assist machine can help clear secretions (phlegm) that they struggle to cough up on their own. Using an Ambu bag regularly can also help preserve strength in the chest wall muscles. Because of these breathing difficulties, chest infections happen more often in children with DMD, and these are usually treated with antibiotics.
Feeding difficulties can also develop. If this happens, a nasogastric tube or a gastrostomy tube may be used to help your child get enough nutrition.
Bladder problems are common in muscle disorders like muscular dystrophy. Your child, or you, may experience urinary incontinence, which means passing urine by accident. This usually happens because the pelvic floor muscles and core muscles have weakened. The risk is higher for those who have limited mobility and who spend long periods sitting down. Pelvic floor exercises can help, and medication is sometimes used for a sudden, urgent need to urinate.
Bowel problems are also common and can include long term constipation, sudden diarrhoea with little warning, or bowel incontinence. Drinking less water than recommended, often done to avoid needing the toilet frequently, can lead to dehydration, which in turn makes constipation and other bowel problems worse. Taking a gentle laxative such as Lactulose regularly through the week can help keep things more comfortable.
At some point, you may want to consider hospice or palliative care to support you or your child in coping with the condition. This kind of care can offer help such as counselling and pain management, alongside the medical care your child already receives.