What is Duchenne muscular dystrophy?
Duchenne muscular dystrophy (DMD) is a type of muscular dystrophy, a rare genetic disorder that causes muscles to become weak and waste away. DMD is the most common and most severe type of muscular dystrophy. About one in 5,000 boys have DMD. Girls rarely have DMD.
Most babies with DMD do not show signs of the condition for a few years. Infants and young toddlers with DMD may reach milestones (crawling, standing, and walking) late. Speech milestones can be delayed in some children.
As DMD progresses, muscles in the hips become weaker, causing children to waddle (hips sway from side to side) as they walk. By the time they’re 12, most children with DMD need a wheelchair to get around.
Lucas receives gene therapy for DMD and finds his super muscles
The first patient in the state to receive a new gene therapy is a trailblazer for children with Duchenne muscular dystrophy.
Duchenne Muscular Dystrophy | Symptoms & Causes
What are the symptoms of DMD?
The first signs of DMD usually appear between the ages of 2 and 3. Many of the symptoms are related to muscle weakness, usually beginning in the legs and later affecting the arms, lungs, and heart.
Symptoms include:
- Trouble getting up from a lying or sitting position
- Frequent falls
- Difficulty running, hopping, and jumping
- Trouble climbing stairs
- Walking on toes or balls of feet
- Waddling walk
- Delayed growth
- Difficulty breathing
- Scoliosis (a curved spine)
- Enlarged calf muscles
- Cardiomyopathy (damaged heart tissues that prevent the heart from beating properly)
What causes DMD?
DMD is caused by a genetic mutation that interferes with the body’s ability to produce a protein called dystrophin. This protein maintains muscle structure. Without dystrophin, muscles break down and become weak.
The mutation that causes DMD is present at birth. DMD often occurs in families with no known history of muscular dystrophy. Girls and women can carry the gene mutation that causes DMD and unknowingly pass it to their children.
Duchenne Muscular Dystrophy | Diagnosis & Treatments
How is DMD diagnosed?
Your child’s doctor will start by examining your child. They may ask you about any signs of muscle weakness or development delays, when you first noticed them, and if anyone in the family has muscular dystrophy. They will then likely order a number of tests.
Tests for DMD include:
- Blood testing to measure creatine kinase (CK), a type of enzyme in the muscles. A high level of CK in the blood could indicate muscle damage.
- Genetic testing to look for mutations in the blood.
- Electrocardiogram (EKG) to test for abnormal heart rhythms and Echocardiogram to test for damage of the heart muscle.
Muscle biopsy and an electromyogram (EMG) may be used to test muscle weakness, however, as genetic testing has become more widespread, these two tests have been used less often.
How is DMD treated?
Most treatments for DMD focus on slowing the progression of the disease, maintaining function, and managing symptoms. Children with DMD need to be seen regularly by lung and heart specialists to manage breathing problems or heart problems.
Your child’s treatment will depend on the severity of DMD, but may include:
- Glucocorticoids (we can choose from prednisolone, deflazacort, and newly approved vamorolone). These are steroids that may slow the loss of muscle strength. They can also delay the development of scoliosis and prevent the need for spine surgery.
- Exon skipping therapies to restore a truncated but functional dystrophin protein given by intravenous infusions. (Currently exon skipping 45, 51, 53 therapies are FDA approved.)
- Heart medicine, such as ACE inhibitors, can slow the progression of heart disease.
- Respiratory care to help with breathing.
- Physical therapy, including stretching, massage, and targeted exercise, can help keep muscles strong and flexible.
- Occupational therapy can help maintain independence by working on fine-motor skills and modifying the environment.
- Bracing may include ankle-foot braces or hand braces worn at night to prevent muscle contractions.
- Surgery to treat related conditions such as muscle contractures, scoliosis, or heart problems.
- Speech therapy to address problems with swallowing or speech.
Gene therapy
In June 2023, the FDA approved a gene therapy for patients with DMD between 4 and 5 years old who met certain criteria. This treatment addresses the underlying cause of DMD by enabling the body to make a shortened version of dystrophin (microdystrophin), the protein that DMD inhibits. Learn more about gene therapy and contact gene.therapy@childrens.harvard.edu for more information.
How we care for DMD at Boston Children’s Hospital
At Boston Children’s Hospital, you and your child will have access to clinicians with experience in all aspects of diagnosing, monitoring, and treating DMD. Our team includes specialists from neurology, genetics, pulmonology, cardiology, endocrinology, orthopedics, physical therapy, occupational therapy, nutrition, and rehabilitation medicine. We maintain long-term care relationships with many of our patients, monitoring their condition and modifying treatment strategies as their needs change. Our goal with every patient is to help them have the best possible quality of life.
In addition to ongoing care, our patients benefit from our ongoing research. Many of the genes responsible for muscular dystrophies and other neuromuscular disorders were found right here at the Boston Children’s Neuromuscular Center. Today, the researchers who made these discoveries are continuing to learn more and are working to develop treatments. In fact, we are one of a few sites in the United States funded by the National Institutes of Health (NIH) to conduct clinical studies on muscular dystrophy.
