What Is Duchenne Muscular Dystrophy?

Duchenne muscular dystrophy (DMD) is a severe, progressive neuromuscular disease that affects the muscles. Caused by a defective gene and first appearing in childhood, DMD results in weakness and muscle loss that gets worse over time.

There is no cure for DMD. Many people with the condition do not live beyond their 30s. Treatment has come a long way, though, adding years to the lives of people with DMD.

This article will explore how DMD develops, what symptoms to expect, and how the condition is treated.

Duchenne Muscular Dystrophy Symptoms

Although a person is born with the gene mutation that causes Duchenne muscular dystrophy, symptoms are not usually noticed until ages 2 or 3, when children start to walk and move around more independently.

The earliest symptoms can include waddling, difficulty walking, and frequent falling. As the condition progresses, many children with DMD will become dependent on a wheelchair. This usually occurs by around the age of 10.

The symptoms that appear depend on how far the disease has progressed and which muscle groups the damage has spread to.

Common symptoms of DMD include:

• Clumsiness
• Weakness
• Delayed onset of sitting or walking in infancy
• Other delays in motor development
• Enlarged calf muscles
• Using hands to get up off the floor (Gower's maneuver)
• Progressive enlargement of the heart (cardiomyopathy)
• Scoliosis (curvature of the spine)
• Contractures (joint tightness)
• Shortness of breath
• Swelling in the legs or feet
• Intellectual or learning disabilities

As the disease progresses, severe and even fatal complications can occur as muscle weakness affects the heart and respiratory systems. Many people with DMD die from cardiac or respiratory failure.

Causes

DMD is a condition that you are born with. It's caused by a mutation in the largest human gene, the DMD gene. The gene produces a protein called dystrophin that muscles need to be able to work properly. Without new supplies of the protein, muscle cells become damaged, grow weaker, and eventually waste away (atrophy).

The gene mutation that causes DMD is an X-linked recessive disorder, which means that it is passed down from mother to child.

Males—who only have one X chromosome—can develop the condition with just one copy of the damaged gene, while females with just one altered gene can be carriers of the mutation, without having active disease. The genetic pattern means that DMD is more common in boys than in girls.

Diagnosis

The diagnosis of DMD begins with a physical examination and review of your personal and family medical history. If you have a known family history of DMD, genetic testing may have already been done.

Other tests that can be used to diagnose DMD include muscle biopsies and blood testing to look for specific proteins and enzymes that can reveal muscle damage caused by the disease.

Once you are diagnosed, different tests will be used to evaluate the progression of the disease, especially to watch for the effects of the disease on the heart or lungs.

Treatment

There is no cure for DMD, but treatment options have improved in recent decades. People who get optimal care have had years added to their lives. A number of clinical trials are in progress, and researchers are even exploring gene editing as a treatment option for DMD.

The main DMD treatments focus on addressing muscle weakness and the damage to the heart or lungs that can cause fatal complications. Examples of medications that are used to treat DMD include:

• Steroids to slow muscle loss
• Albuterol (a medication often given to people with asthma)
• Amino acids
• Carnitine (chemical compound involved in metabolism)
• Coenzyme Q10 (an antioxidant)
• Creatine (amino acid in muscles and the brain)
• Fish oil (rich in omega-3 fatty acids)
• Green tea extracts
• Vitamin E

New types of medications are also being approved, the most recent being an injection called Amondys 45 (casimersen). The Food and Drug Administration (FDA) approved the treatment, which can increase dystrophin production in skeletal muscles, in May 2021.

Other newer medications for DMD include:

• Emflaza (deflazacort), a type of oral steroid
• Exondys 51 (eteplirsen), an injection/intravenous medication to increase dystrophin production
• VYONDYS 53 (golodirsen), an intravenous medication to increase dystrophin production

There are also other medications and treatments in various phases of clinical trials that are being explored as potential DMD treatments.

Prognosis

In the past, children with DMD rarely survived beyond the teen years and often needed mechanical ventilation by age 20 because of weakness in their respiratory muscles. While the life expectancy for people with DMD has increased with improved treatments, most people with the condition are only expected to survive until they are between the ages of 20 and 40.

Coping

Duchenne muscular dystrophy is a progressive disease, which means that the symptoms will get worse over time. People with the condition will experience a gradual loss of function and increasing reliance on others around them for care and support.

DMD can also be challenging for the family and friends of someone with the condition. As DMD progresses, a person's needs will increase, and it can be difficult for their loved ones to provide constant and ever-increasing care.

There are many organizations that support and resources to people with DMD as well as their caregivers, including:

• Muscular Dystrophy Association (MDA)
• The Duchenne Registry
• Coalition Duchenne
• Cure Duchenne
• Jesse's Journey
• Jett Foundation
• Parent Project Muscular Dystrophy
  

Summary

Duchenne muscular dystrophy is a progressive, genetic condition that mostly affects men. While women can inherit the gene, they are usually only carriers and do not have active symptoms.

Over time, DMD causes muscle weakness and eventually muscle loss. Early on, a person will have motor delays and falls. In later stages of the disease, a person will often develop heart and lung complications that are ultimately fatal.

A Word From Verywell

People who inherit an active form of DMD will face progressive weakness and may not live past the age of 40. If you have DMD, working closely with your medical team and having a strong support system are important for both you and your loved ones.

There is no cure for DMD, but ongoing clinical trials and research are adding years to the lives of people with DMD by slowing the progression of the disease. New medications and therapies like gene editing hold promise for more progress in adding to the life expectancy for people with DMD.