Duchenne Muscular Dystrophy In Children

Key points about Duchenne muscular dystrophy

• muscular dystrophy (MD) refers to a group of conditions that cause muscle weakness that gets worse over time
• it's caused by changes (mutations) in genes that are inherited
• Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy
• signs usually appear between 1 and 3 years of age
• it mostly affects boys
• there's no cure for DMD, but there are treatments and support to help manage the condition

What is Duchenne muscular dystrophy (DMD)?

DMD is the most common form of muscular dystrophy. It’s a genetic condition that mostly affects boys. Because of a genetic change, the muscles do not form normally, leading to weakness and damage. 

DMD is a condition that gets worse over time. Boys get better with their motor skills in early childhood but become weaker over time. Eventually, when walking becomes more difficult, boys need to use a wheelchair. Medicines like steroids and support from a medical team may help with your child’s walking.

As DMD progresses, breathing and heart problems develop. Boys with DMD have a shortened life span, mostly due to these issues. But with medical support, young people with DMD can live into their 30s, and some men with DMD live into their 40s or 50s.

Treatment for DMD is changing a lot. New treatments are becoming available, so having a supportive medical team is important.

There is a related condition called Becker muscular dystrophy (BMD). This is similar to DMD but less severe. Many boys with BMD don’t need any particular treatment. A medical team will often monitor them to make sure they stay healthy.

Causes of DMD

DMD is caused by a change (mutation) in the DMD gene. This gene is on the X chromosome. 

A boy with DMD may inherit the gene mutation from his mother, even though she doesn’t have the condition herself. Or, he could have a spontaneous change in the DMD gene - it just happens and hasn’t been inherited from his mother.

This error in the gene means that boys cannot make normal dystrophin. Dystrophin is a protein that is important for normal muscle growth and function. Not having normal dystrophin leads to weak and damaged muscles. This affects the muscles that help us move (skeletal muscles) and the muscles of the heart and lungs. 

Symptoms of DMD

Symptoms usually begin between 1 and 3 years of age. Early signs in tamariki may include:

• delays in reaching motor milestones, such as sitting and standing on their own
• difficulty getting up off the ground or going up steps
• difficulty running or running more slowly than other tamariki
• a waddling walk, which is slower than other tamariki
• toe walking
• bigger calf (lower leg) muscles

As time goes on, some boys will get better at running and jumping, particularly with treatment. But, boys with DMD eventually  become weaker. Most boys will start needing to use a wheelchair between the ages of 10 and 12 years, but this can vary from child to child.

As they get older, boys with DMD get weakness in their arms. This affects their ability to lift and hold things. Eventually, boys with DMD get issues with their heart and lung function. But, things like physiotherapy, medicine and breathing support devices can help. 

Tamariki with DMD may also have problems with learning.

All of these symptoms need management by a range of health professionals, called a multidisciplinary team (MDT). 

Diagnosis of DMD

If doctors suspect your child has DMD, they will examine your child and ask you about their symptoms. They may arrange some of the following tests to confirm the diagnosis. 

Creatine kinase (CK)

This is a blood test. CK is a protein in muscles. When muscles are damaged in DMD, CK gets released into the blood stream. Usually, in DMD, the CK level is very high. This isn’t harmful on its own, but strongly supports a diagnosis of DMD.

DMD genetic testing

This is usually a blood test. This is how health professionals find the change (mutation) in the DMD gene. This test can often confirm the diagnosis of DMD. Health professionals can use this information to check if other people in your family have the same change in their genes.

Muscle biopsy

Diagnosis of DMD doesn’t usually require a muscle biopsy. A muscle biopsy involves taking a small sample of muscle, usually from the thigh. The doctor will send this to the lab where they will examine the structure of the muscle. 

Treatment for DMD

Managing symptoms and preventing complications

There is no cure for DMD. Treatment focuses on managing symptoms and keeping people as strong as possible for as long as possible. Treatment also focuses on preventing complications of muscle weakness, reduced movement, and heart and breathing difficulties.

Steroid medicines

Steroid medicines help slow muscle damage and weakness and are an important part of DMD treatment. Boys with DMD should begin steroid treatment before they start to lose motor skills. Steroids medicines can cause side effects. Your child’s health professional will monitor for side effects and manage them if they happen. In general, the benefits of being stronger and maintaining walking with steroid medicines outweigh the side effects.

Steroid Management Plan For Children With Duchenne Muscular Dystrophy

Other supportive treatments for DMD

Physiotherapy and occupational therapy

Physiotherapy can help your child maintain muscle function. It’s good to start exercises and stretching early on. This can help keep your child’s muscles flexible and strong.

Occupational therapy can help your child learn new ways of doing things. An occupational therapist can make adjustments to your home and give you equipment to support your child.

Support aids 

Support aids such as splints or braces can help with your child’s stability and mobility.

Your child can use scooters and wheelchairs when walking becomes harder.

Medicines and surgery

There are medicines that can help keep the bones and heart healthy. Surgery can help with contractures of the muscles and tendons, or spinal curves. 

Breathing support

Breathing exercises can help with breathing problems. Ventilation support may be necessary once the breathing muscles are affected.

Clinical trials 

Many clinical trials are happening all around the world to find better treatments and potentially a cure for DMD. To make sure you have the chance to be part of any trials that come to Aotearoa New Zealand, it’s a good idea to register with the New Zealand Neuromuscular Disease Patient Registry.

Caring for a child with DMD

Treatment for DMD is changing a lot, and tamariki with DMD are living longer, more active lives than those diagnosed 20 years ago. The treatment available will continue to change, so having support from your medical team is important.

Boys with DMD usually have frequent appointments with a variety of health professionals. There are good international guidelines for health professionals to follow for monitoring and treating DMD.

Because boys with DMD can have learning difficulties, it’s essential to work with school teachers and support staff. This can help boys with DMD get the most out of their education.

To prevent infections, it's important for tamariki to be vaccinated against pneumonia and to keep up to date with flu and COVID-19 vaccinations.

Support for DMD

There is also a Kiwi Kids with DMD Facebook support group that offers peer connection and shared experiences.

Manifesting carriers of DMD or BMD

Females who carry the affected gene usually don’t have symptoms themselves but can pass the gene on to their tamariki. A manifesting carrier is a female who carries the affected gene and also has symptoms of muscle weakness. This can happen with no known family history of DMD. Females with any symptoms which suggest muscular dystrophy should have a test.  

Manifesting carriers may have heart or breathing problems, particularly later in life. If untreated, these heart problems can be serious, so it’s important that mothers of boys with DMD have a test.