• Duchenne muscular dystrophy (DMD) can cause symptoms within the first few months or years of a child’s life.
• DMD often leads to developmental delays, muscle weakness, problems with learning or behavior, and abnormal blood work results.
• Genetic tests are the primary tool for diagnosing DMD, although physical exams and blood tests may help doctors first recognize that there’s a problem.

Duchenne muscular dystrophy is a rare disease that affects the skeletal muscles — that is, the muscles throughout your body that allow you to move. The condition is caused by a mutation (change) in a gene that’s integral to producing a protein called dystrophin, which helps muscles work properly.

Although the gene mutations that cause DMD are present at birth, major symptoms don’t typically appear for the first couple of years of a child’s life — most often when a child is between the ages of 3 and 5. Over time, the condition progresses, eventually leading to new and worsened symptoms.

It’s often not obvious right away when a child has DMD, even though minor developmental issues may appear early on in their life. Many different factors, including other genetic disorders, medical conditions, or environmental factors, can cause a child to grow and develop more slowly than expected.

Additionally, even though DMD can be caused by genetic factors, many people with the condition don’t have a family history of the condition. This means that, when a child displays their first symptoms, it’s often not immediately apparent that DMD is the cause.

Which Symptoms May Signal DMD?

Certain symptoms tend to appear early on within the course of DMD. Here are some of the symptoms you may want to watch out for in your child.

1. Developmental Delays

Health experts use developmental milestones to determine whether a child is growing and developing as expected. These milestones describe when, on average, children tend to start displaying certain motor skills, thinking abilities, or behaviors.

One of the first signs of DMD is if your child misses developmental milestones. In a study of young males with DMD, researchers found most started missing milestones by the time they were 2 or 3 months old, and they tended to miss increasingly more as they got older. For example:

• About 22 percent of the males couldn’t lift their head while lying down by the time they were 3 months old.
• Just over half were unable to walk by themselves by the time they reached 18.5 months.
• About 4 out of 10 were unable to say two-word sentences at 25 months old.

Missing milestones isn’t always a sign of a serious condition like DMD. Children develop at different rates, and many healthy children hit milestones later than expected. However, if you regularly notice signs that your child isn’t developing at the same rate as their peers, it may be time for a conversation with their pediatrician.

2. Weakened Muscles

One of the main symptoms of DMD is progressive muscle weakness. Decreases in muscle strength often first affect your child’s hips and legs but may also impact the arms or neck.

Younger children may not be able to hold up their head as well as expected. They may have difficulty crawling, walking, or going upstairs.

As your child gets older, you may notice that they can’t move around or play in the same way as other children their age. Your child may also walk unusually — for example, they may walk on their toes, waddle, or have an arched back.

Another sign of DMD-related muscle weakness is Gowers’ sign, a maneuver in which a child walks their hands up their legs as they stand up. Mobility and balance issues, such as frequent falls or tripping, may also signal DMD.

These issues develop when muscle fibers aren’t as strong as they need to be. They may also be caused by contractures (stiffened or shortened muscles) or scoliosis (a curved spine).

Muscle problems may change the appearance of muscles. Many kids with DMD have enlarged calf muscles, making their lower legs look wider or more muscular than expected. However, muscles in the abdomen, shoulders, pelvis, and upper legs may atrophy (become smaller).

3. Problems With Learning or Behavior

About 1 in 3 kids with DMD have signs of cognitive impairment (difficulties with thinking or memory abilities) that can impact their quality of life. These symptoms may include:

• A reliance routines and feeling very stressed when things change
• Difficulty communicating
• Social difficulties, such as having trouble making friends or playing
• Frequent time alone
• Irritability, anger, or negative thoughts
• Anxiety
• Problems focusing
• Poor memory
• Poor academic performance

Children with DMD are more likely to be diagnosed with learning disabilities, attention-deficit/hyperactivity disorder (ADHD), and autism.

4. Abnormal Blood Work

Early on in the disease course — during early childhood or even infancy — your child may have unusual results for certain blood tests. They may have very high levels of an enzyme called creatine kinase as well as higher-than-expected levels of liver enzymes, including aspartate transaminase and alanine transaminase.

Tests That Help Confirm DMD

What do you do if your child is starting to show some of these symptoms? It’s a good idea to talk to your child’s doctor or to a provider that specializes in muscle disorders in children. Your pediatric health care team can recommend several tests, including some of the below, that can diagnose or rule out DMD and other related conditions.

Other tests aren’t used during the initial diagnosis of DMD but may be needed later on to look for complications of the condition. A complication is a second condition that develops while you are living with a first condition. Your child’s doctor may recommend ongoing testing to look for DMD complications.

Physical Exam

During an initial physical exam, the pediatrician will ask you or your child about possible symptoms. They may ask how long these symptoms have been occurring and inquire about other health issues your child has experienced in the past.

The pediatrician may also conduct a neurological exam and muscle exam. This involves performing tests to see how well your child’s nerves and muscles are working. Typical signs include Gowers’ sign, large calf muscles, and a tendency to walk on their toes.

Creatine Kinase Test

This test can help diagnose tissue damage. Levels of creatine kinase, an enzyme normally found in your muscle cells, increase when the muscles are harmed by injury, inflammation, or muscle diseases like DMD or rhabdomyolysis.

A creatine kinase test alone can’t diagnose DMD, but it can show when there are problems with the muscles. Your pediatrician will likely use this as a first step in determining that your child’s muscles are affected by a health condition.

Genetic Tests

Once your child’s doctor has determined that your child is experiencing muscle problems, they may recommend genetic testing. This type of test is the most helpful in telling you for sure whether your child has DMD.

There are a few types of genetic tests that your doctor may recommend. These tests identify changes in the dystrophin gene, which causes DMD. If genetic testing shows that your child has a DMD gene mutation, your doctor may also recommend testing other people in the family to see if they also carry these mutations.

One organization, Parent Project Muscular Dystrophy, offers free genetic testing and genetic counseling for muscular dystrophy to people living in the U.S. or Canada.

Muscle Biopsy

Muscle biopsies may be useful when genetic testing can’t find a mutation that causes DMD. During this process, your doctor will take a small sample of muscle tissue and send it to a laboratory for further study.

Multiple types of tests — including immunofluorescence, immunostaining, or Western blotting — may be performed on the muscle sample. These tests show whether the dystrophin protein that causes DMD is present or absent within muscle tissue. However, genetic testing usually uncovers any relevant gene changes, so muscle biopsies aren’t often needed for most people with this neuromuscular disease.

Electrocardiogram

Most people with DMD don’t initially have symptoms that affect the heart. However, cardiomyopathy (disease of the heart muscle) typically develops later in the course of the disease.

An electrocardiogram can help detect cardiomyopathy and other DMD-related heart problems. This test measures electricity in your heart, telling you whether it’s beating normally and detecting damage to your heart muscle.

Talk With Others Who Understand

On myDMDcenter, people with Duchenne muscular dystrophy and their loved ones come together to gain a new understanding of DMD and share their stories with others who understand life with DMD.

Have you or a loved one been diagnosed with DMD? What was the diagnosis and testing process like? Share your experiences in the comments below.