What Is Muscular Dystrophy (MD)?

Medically reviewed by Nicholas R. Metrus, MD

"Muscular dystrophy" is an umbrella term for a group of neuromuscular disorders that cause progressive muscle weakness and lack of physical function over time. Depending on the type of muscular dystrophy, the condition can be detected in childhood or adulthood.

This article will review types and causes of muscular dystrophy, how it is diagnosed and treated, and the outlook for condition progression and management.

Types of Muscular Dystrophy

Muscular dystrophy leads to worsening muscle weakness over time. While there are nine different types of MD, the two main types are:

• Duchenne muscular dystrophy: This type typically starts in boys between the ages of 2 and 6, characterized by general muscle weakness and muscle wasting (atrophy) that affects all muscles, especially the arms and legs. Duchenne muscular dystrophy is the most common form, making up approximately 50% of all cases.

• Becker muscular dystrophy: This type typically starts later in life, during adolescence or early adulthood, characterized by muscle weakness and muscle wasting that progresses slowly.

Other types of muscular dystrophy include:

• Congenital muscular dystrophy: Occurs at or near birth, causing widespread muscle weakness throughout the body

• Distal muscular dystrophy: Affects the muscles at the ends of the limbs, including those in the forearms, hands, lower legs, and feet

• Emery-Dreifuss muscular dystrophy: Slowly progressing wasting away of the muscles of the upper arms and legs, often occurring with contractures

• Facioscapulohumeral muscular dystrophy: Affects the muscles of the face, shoulder blades, and upper arms

• Limb-girdle muscular dystrophy: Muscle weakness and wasting of the muscles of the hips and shoulders (limb girdles)

• Myotonic dystrophy: Affects the muscles of the eyes and other organ systems, ncluding the heart and gastrointestinal (GI) tract

• Oculopharyngeal muscular dystrophy: Affects the muscles of the eyes and mouth

How to Detect MD: Signs and Symptoms

Symptoms of MD occur gradually and tend to worsen over time. Muscle weakness and atrophy are the most common symptoms that occur with all types of muscle dystrophy.

Depending on the area of the body affected, you may find it gradually become more difficult to perform everyday movements and activities like walking, standing up from a chair, and getting dressed. Your balance may be affected and you may also experience a lack of coordination.

Other symptoms that can occur alongside muscle weakness and wasting include:

• Leg pain

• Clumsiness

• Weakness in the face, arms, or shoulders

• Heart or lung problems

Muscular Dystrophy Causes

All forms of MD are genetic, resulting from mutations (changes) that affect certain genes that control muscle function. Most of these genetic mutations are inherited, although some can occur spontaneously.

The three types of inheritance patterns linked to the development of MD are:

• Autosomal dominant: A genetic mutation is inherited from a parent with the condition.

• Autosomal recessive: A genetic mutation is inherited from both parents who are carriers of the gene. Neither parent has the condition.

• X-linked recessive: A genetic mutation is inherited from one parent via an X chromosome. Because females have two X chromosomes and males have one X and one Y chromosome, males are more likely to exhibit symptoms if they inherit a genetic mutation on an X chromosome.

Learn More:Causes and Risk Factors of Muscular Dystrophy

Because muscular dystrophy is a genetic condition, lifestyle factors cannot reduce your risk of developing the condition. Being underweight, having poor lung function, and having a high amount of protein in the blood, however, can damage the heart with this condition. These factors increase the risk of complications and early death for those who have MD.

How Does Muscular Dystrophy Progress?

Muscular dystrophy is a progressive condition, meaning that symptoms get worse over time. How quickly muscular dystrophy progresses depends on both the type of muscular dystrophy you have as well as how much you are actively engaged in your treatment. Staying actively involved in regular physical therapy and exercise can maintain muscle strength and function to keep you as physically active and independent as possible.

While progression of the condition is often inevitable, specialized equipment like assistive devices for walking, wheelchairs, and adaptive equipment for hand and arm use can be used to help maintain independence with daily activities.

How Is Muscular Dystrophy Diagnosed?

Diagnosing muscular dystrophy begins with a visit to your healthcare provider, with whom you will discuss your or your child's personal and family medical histories and symptoms. Your healthcare provider will likely recommend different diagnostic tests to help determine if you have muscular dystrophy and rule out other conditions that can also cause muscle weakness.

These tests include:

• Blood work to assess levels of enzymes and inflammatory markers

• Genetic testing to assess for genetic risk

• Muscle biopsies to examine the quality of your muscle tissue

• Magnetic resonance imaging (MRI) of your brain, spinal cord, and muscles to assess for damage

• Electromyography (EMG) testing to assess the electrical activity of your muscles

• Nerve conduction tests to assess how signals travel from your nerves to your muscles

• Electrocardiograms (ECG) and echocardiograms (echoes) to examine your heart function

Muscular Dystrophy Treatment

While there is no cure for muscular dystrophy, several treatment options can help manage symptoms and improve quality of life.

Medications

Certain medications can help lessen damage to muscle cells and decrease symptoms like muscle spasms. These include glucocorticoids, immunosuppressants, and anticonvulsants. Other medications like beta blockers and angiotensin-converting enzyme (ACE) inhibitors may also be used to treat heart problems.

Assistive Devices

Muscle weakness from muscular dystrophy often affects large muscles of the legs, which can make it difficult to maintain balance and walk. Using an assistive device like crutches, a walker, or a wheelchair can help maintain independence with mobility.

Physical Therapy

Physical therapy can teach you exercises and provide techniques to strengthen muscles and improve balance, coordination, and functional movements like transfers (moving from one surface or area to another) and walking. Physical therapy can help maintain as much function as possible to preserve the muscle strength needed for everyday activities.

Muscular Dystrophy Complications

Progressive muscle weakness and wasting that occurs with muscular dystrophy can lead to several complications. These include:

• Mobility problems, resulting in difficulty walking and the need for an assistive walking device or wheelchair

• Muscle contractures that can be painful and limit normal range of motion needed to move parts of the body

• Breathing problems from weakness of the diaphragm and other muscles involved in respiration

• Scoliosis (sideways curvature of the spine) and spinal instability

• Heart problems, requiring cardiac medication and/or surgery to improve function

• Difficulty swallowing/eating, which can lead to nutritional deficiencies and infections via aspiration pneumonia

• Cognitive changes and learning difficulties

Muscular Dystrophy Support and Resources

Living with muscular dystrophy or with a loved one with muscular dystrophy can be challenging, but you shouldn’t have to go through it alone. Nonprofit organizations like the Muscular Dystrophy Association provide helpful educational resources, support research efforts and clinical trials, and can connect you with support services.

The Centers for Disease Control and Prevention (CDC) also provides a list of helpful resources on its website.

Related:What to Know About Muscular Dystrophy in Children As a Parent

Outlook for Muscular Dystrophy

The life expectancy for people with muscular dystrophy varies depending on what type of muscular dystrophy they are diagnosed with. Some people can live a full and fulfilling life and live as long as people who do not have muscular dystrophy, while others can have a reduced life span, especially if the heart and diaphragm are affected. Early diagnosis and treatment are key for extending life expectancy for those diagnosed with muscular dystrophy.