Duchenne Muscular Dystrophy (DMD)

Duchenne muscular dystrophy (DMD) is a progressive condition that causes muscles to get weaker over time. It mainly affects the muscles used for movement, breathing and heart function.

It’s inherited and it typically affects males. Symptoms usually start in early childhood and slowly get worse. You might notice developmental delays, toe walking or muscle weakness in your child as they grow.

This disease affects about 1 in every 3,600 male infants. It’s the most common form of muscular dystrophy and the leading type of severe inherited muscle disorder (myopathies).

While there’s no cure, and it will shorten life expectancy, treatments are available to slow its progression and help your child manage symptoms.

Duchenne muscular dystrophy symptoms

DMD symptoms worsen over time and may include:

• Muscle weakness
• Stiff joints
• Developmental delay, like saying their first words and sitting up
• Fatigue
• Loss of muscle bulk

Muscle weakness can affect how your child walks and moves. You might notice these signs:

• Difficulty climbing stairs, running or jumping
• Frequent falls
• Increase in calf muscle size
• Toe walking
• Using their arms to push themselves up from the ground
• Waddling

Symptoms of DMD usually appear between the ages of 2 and 4. They can start as early as infancy, but you might not notice them until later in childhood.

Duchenne muscular dystrophy causes

A genetic variant causes Duchenne muscular dystrophy. This gene tells their body how to make a protein called dystrophin. Dystrophin keeps muscles strong and protects them when they move.

If your child has this condition, their body makes little or no dystrophin. Without it, their muscles become weak and start to break down. Over time, muscle cells die, and their body can’t replace them. Instead, the empty spaces fill with fat and scar tissue. This makes movement even harder.

Duchenne muscular dystrophy inheritance

DMD is usually passed down through families. It’s X-linked recessive. Here’s how that works.

The gene that causes it is on the X chromosome. This is one of the two sex chromosomes:

• Boys have one X and one Y chromosome (X comes from mom, Y comes from dad).
• Girls have two X chromosomes (one X from each parent).

As boys only have one X chromosome, if that X chromosome has the gene change that causes DMD, they’ll have the disease. This is because they have no backup copy on another X chromosome to make up for it. Girls, on the other hand, have a backup copy on their other X chromosome and typically won’t be affected.

Girls either don’t have symptoms or they’re very mild. Girls may become carriers. Carriers inherit the gene change but don’t have symptoms. They may pass the gene on to their future children.

However, in about 3 out of 10 cases, the gene change happens randomly. This means it wasn't passed down and there wasn’t a family history. There’s no way to prevent Duchenne muscular dystrophy.

How doctors diagnose Duchenne muscular dystrophy

If your child shows signs, see their pediatrician. Their provider will do a physical, neurological and muscle exam. They’ll also ask about your child’s symptoms and medical history.

If they think it’s DMD, their provider may refer you to a pediatric neurologist or order these tests to confirm a diagnosis:

• Creatine kinase (CK) blood test: High CK levels suggest muscle damage. In DMD, levels can be 10 to 20 times above normal by age 2.
• Genetic test: This confirms the condition by checking for missing or faulty dystrophin genes.
• Muscle biopsy: A small muscle sample (usually from their thigh or calf) helps their provider look for DMD-related changes.
• Electrocardiogram (EKG): This test checks your child’s heart function, as this disease often affects the heart.

How is Duchenne muscular dystrophy treated?

There’s currently no cure for DMD. The main goal of treatment is to manage symptoms and slow progression. Supportive therapies may include:

• Steroid medications: Prednisone or deflazacort may slow muscle damage and help maintain strength and independent movement, breathing and heart function.
• Steroid alternatives: Vamorolone helps fight inflammation in the muscles and heart cells, which may help protect them from damage. This helps maintain mobility and strength longer.
• Gene-based therapy: Medications like eteplirsen, delandistrogene, golodirsen, casimersen and viltolarsen help their body produce a shorter but functional form of dystrophin. Some of these only work for certain types of variants that cause DMD.
• HDAC inhibitor: Givinostat is a medication that helps turn on genes that repair and grow muscles and reduce fibrosis (scar tissue). This may slow muscle function decline.
• Heart care: ACE inhibitors or beta-blockers may protect their heart. Regular check-ups and heart imaging usually begin around age 6.
• Physical therapy: Stretching and exercises can prevent joint and muscle issues. Therapists may also recommend braces, splints or mobility aids.
• Nutrition: Calcium and vitamin D supplements support bone health. A nutritionist can help ensure balanced meals throughout the day.
• Exercise: Light activities like swimming or supervised play keep muscles active. Your provider can guide you on what’s safe.
• Breathing support: Devices like a BiPAP or ventilator may help over time with breathing, especially during sleep.

When should my child see their healthcare provider?

If your child has this condition, they’ll need regular visits with their care team to manage treatment and track symptoms. You’ll get to know their providers well, as ongoing care is essential. As your child grows and their symptoms change, their treatment plan may need to adjust, too.

What can I expect if my child has Duchenne muscular dystrophy?

This disease is progressive despite treatment. That means it gets worse over time. The outlook is poor, as it shortens your child’s lifespan.

You can expect that your child will need to use a wheelchair by their 12th birthday. But this loss of mobility shouldn’t take away from their ability to play and enjoy childhood moments.

Duchenne muscular dystrophy life expectancy

People with this condition typically live into early adulthood, though life expectancy varies. Advances in treatment and supportive care have helped many live longer than once expected.

Most face complications related to their heart or breathing. In some cases, issues like pneumonia or airway blockages can also become serious.