Understanding the progression of Duchenne muscular dystrophy

A progressive disease is a disease or health condition that typically gets worse with time. Muscular dystrophies are described as progressive because the loss of muscle strength and muscle mass follow this progressive course, getting worse over time. Some muscular dystrophies progress slowly, others more quickly. Duchenne muscular dystrophy (DMD) is one of the most common types, and also a type of muscular dystrophy that typically progresses quickly.

The first symptoms of DMD begin in early childhood, before the age of six. It primarily occurs in males, and the condition is rare in females. (However, other types of muscular dystrophy occur at later ages, and affect both males and females).

For parents and caregivers of children who have DMD—or who are concerned about DMD and want to better understand the symptoms—it helps to understand how the disease begins and how it progresses.

How DMD affects the muscles

DMD is a genetic disorder. Genes are sections of DNA that contain instructions for assembling the many different chemical compounds that make up the human body. Many genes contain instructions for assembling different proteins.

DMD is caused by a mutation in the gene that contains instructions for assembling a protein called dystrophin. This protein is essential to the strength, repair, and other healthy functions of muscles—including skeletal muscles and cardiac muscles. Without dystrophin, these muscles break down and are replaced with fat tissue and scar tissue.

The progression of DMD

The course of DMD can vary from one person to the next. Many children with DMD appear to develop normally during infancy and early childhood, though there may be some delays. Signs of muscle weakness typically appear between the ages 2 to 3 years:

• A child may have difficulty running, climbing stairs, and getting up from the floor.
• Toe-walking, a waddling gait, and frequent falls may be observed.
• There may also be delays in learning and cognitive development.

During preteen years (ages 6 through 12), muscle weakness and loss of muscle become more prominent and widespread, leading to difficulty with daily activities:

• Scoliosis (abnormal curvature of the spine) may develop during this time.
• Lung function may become impaired as a result of scoliosis, leading to breathing difficulty.
• Children with DMD may require the use of mobility aids such as leg braces and wheelchairs.

Symptoms continue to progress during teenage years (ages 13 to 19). Cardiomyopathy (disease of the heart muscle) may develop during this time. The risk of respiratory complications also increases.

As a person ages from their teens into young adulthood (20s and 30s), mobility may be severely limited, and a person may require full-time care. A person may have a variety of additional healthcare needs to address mobility, breathing, cardiac function, nutrition, and other complications that occur as a result of having DMD.

Despite the challenges that come with DMD, it's important to remember that there are many resources and support systems available for families. People with DMD can live meaningful lives and enjoy fulfilling relationships with their loved ones.

Treatment options for people with DMD are improving, with multiple drugs and therapies approved in the past decade, and more treatments under development.