Symptoms of Duchenne muscular dystrophy
Muscle weakness in Duchenne muscular dystrophy can lead to symptoms related to mobility, coordination, posture, and breathing, as well as other health effects.
Duchenne muscular dystrophy (DMD) is a genetic condition that causes a progressive loss of muscle function. It most commonly affects young males and is often diagnosed early in life, around 4 years of age.
Loss of muscle function in DMD can cause a variety of symptoms that affect mobility, coordination, and development.
As DMD progresses, it causes more severe symptoms, and people may need additional support or intervention. While some treatments can help slow the progression of DMD, the symptoms can eventually affect a person’s independence and life expectancy.
Read on to learn more about the signs and symptoms of DMD across the progression of the disease.
During the first few years of life, infants and children with DMD may experience delays in meeting key developmental milestones, such as walking, crawling, and talking.
In most cases, children with DMD have mild delays and will catch up to their peers. When delays are mild, parents and teachers may not recognize these delays as early signs of DMD.
Some children may have delays in only some developmental milestones, while others may have no delays at all.
As children with DMD get older, they tend to grow more slowly than other children their age, so they may have shorter stature.
DMD causes muscles to break down and can lead to a variety of symptoms related to muscle weakness. Difficulties with mobility and coordination are especially common and may be among the first noticeable symptoms in young children.
Young children with DMD may seem clumsy or fall down often. They may also have trouble climbing stairs, running, or getting up after a fall.
Changes in a child’s gait may be noticeable as well, especially as they get older. Children with DMD commonly walk on their toes, which may cause a waddling gait. They might also walk with their legs wide apart or their chest pushed out in an attempt to help with balance and avoid falling.
Frequent falls may increase the likelihood of broken bones as a child gets older.
One of the earliest recognizable signs of DMD is known as Gower’s sign. This is a maneuver that children with DMD often use to get up off the floor and reach a standing position.
It involves using their hands and arms to push themselves first into a kneeling position and then into a wide-stance standing position. They will then walk their hands up their legs until they are fully standing.
Enlarged calf muscles are common in children with DMD. While it may seem counterintuitive that larger muscles can indicate muscle weakness, the enlargement results from pseudohypertrophy, a buildup of fat and other tissues within the muscle that contributes to muscle weakness.
Pseudohypertrophy can also affect the muscles of the thighs, as well as the tongue or forearms, but it is
If a doctor suspects — as a result of symptoms or family history — that a child has DMD, they may order blood work.
Blood tests can check for changes that suggest DMD, including high levels of markers of muscle damage (such as creatine kinase) and high levels of liver enzymes.
A doctor may order additional DNA testing to confirm the diagnosis of DMD.
As the muscles continue to break down, people can experience muscle and tendon stiffness that may affect their posture. Curving of the spine (known as lumbar lordosis or scoliosis) is common, along with rigidity in the following joints:
While DMD’s effects on the muscles do not typically cause pain, changes in posture may cause muscle cramping or discomfort.
Scoliosis (a sideways curving of the spine) can affect the lungs, making breathing difficult. DMD may also affect a person’s lung function as the condition progresses and the muscles that control breathing become weaker.
Reduced lung function can cause shortness of breath. Some children may not experience any changes in their breathing but may still show symptoms of reduced lung capacity, such as:
Doctors will typically begin monitoring a child’s lung function around 5 years of age to detect early changes in breathing and begin taking steps to preserve lung health.
A doctor will often recommend vaccination against respiratory viruses, such as influenza, because weakness in the muscles that control breathing can increase the likelihood that these viruses will progress to pneumonia.
Children with DMD have low oxygen levels due to lung problems and must exert a lot of effort to overcome their muscle weakness. As a result of both of these issues, they often experience fatigue.
They may become tired easily and have difficulty keeping up with their peers. As the condition progresses, they might also have trouble taking care of themselves.
Eventually, many children with DMD need to use mobility devices to get around. Most children start using a wheelchair at least part of the time by their early teen years.
Using a wheelchair can help conserve energy and reduce fatigue. Many children also experience a renewed sense of independence and vitality with support from mobility devices.
In DMD, a person’s body does not produce enough of a protein called dystrophin, which is important for muscle strength. Dystrophin is present throughout the body, including in the brain.
When there is not enough dystrophin in areas of the brain that regulate attention, memory, and emotions, people may experience a variety of effects on behavior and cognition (thinking ability).
Cognitive effects and learning difficulties
Certain behavioral conditions — including attention deficit hyperactivity disorder (ADHD), autism, and mood disorders — are more common in children with DMD than in the wider population.
As DMD progresses, people will eventually develop cardiomyopathy, which is a weakening of the heart muscles. Almost all people with DMD experience symptoms of cardiomyopathy after 18 years of age.
Cardiomyopathy can contribute to worsening of many symptoms of DMD, including fatigue and breathing difficulties.
Cardiomyopathy can cause serious symptoms and can even be life threatening. Doctors typically recommend early and regular monitoring of heart function, even before symptoms develop, to detect changes and allow for early intervention if possible.
As muscles become progressively weaker in DMD, people may develop a variety of signs and symptoms that can affect their mobility, independence, and overall well-being.
Some treatments can help slow the progression of the condition, but symptom management is still an important aspect of DMD care.
Mobility aids can help reduce fatigue and restore a certain degree of independence. Careful monitoring of heart and lung function is important to detect changes and allow for early intervention as needed. Doctors may recommend vaccination against respiratory infections to help prevent complications from reduced lung function.
If a parent suspects that their child has symptoms of DMD, it is important that they consult a doctor. Getting a DMD diagnosis as early as possible can allow caregivers and doctors to establish a care plan, identify support needs, and potentially slow the progression of the disease.