Congenital muscular dystrophy (CMD)

Congenital muscular dystrophy (CMD) is caused by a change (mutation) in a gene. This mutation leads to a loss of certain glycoproteins in the body's cells, and these glycoproteins are needed for muscles to work normally. Without enough of them, the muscles become more likely to get damaged through everyday use, and they also lose much of their ability to repair themselves afterward.

Doctors don't yet fully understand why CMD causes muscle weakness so much earlier in life than other forms of muscular dystrophy. One possible explanation is that the particular muscle proteins affected by CMD are ones a child's body needs very early in development, while the proteins involved in other types of muscular dystrophy may not be called upon as heavily until later, as the child grows.

In CMD, there are a few tests doctors use to help confirm the diagnosis.

A blood test checks the level of a muscle protein called creatine kinase (CK). In about 40% of congenital muscular dystrophy cases, CK is 5 to 20 times higher than normal.

An EMG tests the electrical activity in the muscles. A small needle is inserted into the muscle to record this activity, and it might show a pattern of abnormal activity. Children might need a general anaesthetic for this procedure.

A muscle MRI might be used to show which muscles are affected, which helps identify the type of CMD. Children might need a general anaesthetic for this procedure.

A muscle biopsy might be used to identify the specific type of congenital muscular dystrophy you have. Children might need a general anaesthetic for this procedure.

A blood test can also be used for genetic testing, which may help identify the type of CMD you or your child has.

There is no cure for CMD, but supportive treatments are available to help manage the symptoms in you or your child.

Some children with CMD do walk. For others, walking is delayed, and they may not walk until they are 5 years old or later. Some children who do walk may lose this ability as they grow older and heavier, because the muscles can find it harder to cope with the strain as the body gets bigger.

Your child might be referred to a specialist for the following:

• physiotherapy to work on muscle strength and flexibility
• physical aids like a walking stick, crutches or a wheelchair
• occupational therapy to help maintain independence
• leg splints to help your child walk

Your child will have regular electrocardiograms (ECGs) to check the heart rhythm, and will also need an echocardiogram from time to time.

Your child might have difficulty feeding. In that case, a nasogastric tube or gastrostomy tube may be inserted to help with feeding.

It is likely your child will have breathing problems and will need a machine to help with breathing at night, and sometimes during the day as well.

For older children, cough assist machines can help them cough up and clear secretions (phlegm). Using an Ambu bag can also help preserve the strength of the chest wall muscles.

Children with CMD face a higher risk of frequent chest infections. These are usually treated with antibiotics.

Bladder problems are common in people with muscle disorders like muscular dystrophy. You might experience urinary incontinence, where urine leaks by accident. This is often caused by weakness of the pelvic floor muscles combined with weakness of the core muscles.

You are more likely to experience urinary incontinence if you:

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

Pelvic floor exercises may help with this. An urgent need to urinate can sometimes be eased with medication.

You might also experience bowel problems such as:

• chronic constipation
• diarrhoea with little warning
• bowel incontinence

If you tend to drink less water than recommended to avoid needing the toilet during the day, this can lead to dehydration, which can worsen constipation and add to bowel problems. Taking a gentle laxative such as Lactulose regularly through the week may help, and medication can sometimes help as well.

Surgery may be used to correct scoliosis or prevent it from getting worse. Tight joints caused by tendon contractures can be loosened by surgically lengthening or releasing the tendons, which should improve movement.

Many children with CMD take part fully in their school activities without being held back by their condition. Others may need extra support to get the most out of their time at school.

You may also want to consider hospice care to help you or your child cope with the condition. Hospice care can offer support such as:

• counselling
• pain management

Read more about palliative care.

Read more about congenital muscular dystrophy.