If you’re the caregiver for someone with Duchenne muscular dystrophy (DMD), you may have noticed your loved one has enlarged calf muscles. This is a common sign of DMD, called calf pseudohypertrophy, and often develops in early childhood as children with DMD begin navigating their world.

Enlarged calves are tied to other physical symptoms of DMD, including muscle weakness and trouble walking. Calf pseudohypertrophy is just one of many symptoms — including scoliosis (curving of the spin) and cardiomyopathy (weakness and deterioration of the heart muscle) — that can cause daily challenges for people with DMD.

This article explains the science behind calf enlargement, how it impacts the lives of people with DMD, and how to cope with the obstacles it presents.

Understanding Enlarged Calves in DMD

It’s important to understand why calf pseudohypertrophy occurs in children with DMD and how many people it affects.

What Causes Enlarged Calves in DMD?

DMD calf enlargement is known as “pseudohypertrophy” due to the nature of the enlargement. To understand pseudohypertrophy, we first need to define “hypertrophy.” The term refers to an increase in the size of individual cells without a change in the number of cells. Skeletal muscle — the type of muscle attached to your bones that you can flex and control voluntarily — is one of the major muscle types in the body where hypertrophy occurs. When you engage in activities like lifting weights, running, and biking, muscle hypertrophy happens as your muscles grow in response to these exercises. This growth improves the strength of your entire muscle group, enabling you to lift more, run farther, and bike harder.

Calf pseudohypertrophy — a common symptom of DMD — may look similar to normal muscle hypertrophy from the outside, but it has the opposite effect. In calf pseudohypertrophy, the calf muscle cells themselves are not actually growing. Instead, calf muscle is being replaced by other kinds of tissue, such as fat and connective tissue, which do not provide functional strength or stability. As a result, although the calves become larger, they also become weaker due to atrophy — the gradual loss of muscle tissue.

How Common Are Enlarged Calves in DMD?

The majority of people with DMD have enlarged calves, with some studies finding this symptom in up to 94 percent of people with the condition. This enlargement typically becomes noticeable in children with DMD between the ages of 3 and 6. Caregivers are often the first to observe this sign, which usually prompts further medical evaluation, such as genetic testing and muscle biopsy, to diagnose DMD.

However, calves are not the only muscle group that can show false enlargement. Individuals with DMD may also experience enlargement in the upper legs, shoulders, hands, diaphragm, and even the tongue. Over time, this can lead to issues with various functions, including posture, upper body strength, swallowing, and breathing.

Impact of Enlarged Calves on Children’s Lives

Now that we understand why this symptom occurs and whom it affects, let’s explore how it impacts daily life.

Motor Skills and Mobility

The enlargement of the lower legs leads to muscle loss and weakening, which can interfere with the development of motor skills. This symptom typically emerges during the toddler years, a critical period when children are learning to navigate their environment and develop physical abilities. As a result, this symptom can make walking and moving challenging, potentially affecting their developmental milestones.

Children with DMD often walk more slowly, take shorter steps, and may lean forward. The enlargement of their calves and other leg muscles can reduce flexibility and strength in the hips, knees, and ankles, making activities such as climbing stairs, rising from a seated position, and walking long distances difficult. They may exhibit a “toe walk,” where they walk on their toes and/or the balls of their feet, and a “waddling gait,” depending on which muscles are affected. Frequent falls, especially when tired, are common.

The severity of these symptoms varies among individuals and depends on factors like age and medical interventions. As DMD progresses, these challenges may worsen, potentially necessitating the use of mobility aids or other interventions.

Psychosocial Effects

In addition to physical challenges, calf enlargement and the resulting mobility issues can impact a child’s self-esteem and social interactions. Children with DMD may experience frustration and embarrassment due to their mobility limitations, which can affect their confidence and social engagement.

Caregivers play a crucial role in supporting the emotional well-being of these children, alongside managing their physical needs. A supportive environment at home and school can help mitigate some of the challenges these children face as they navigate their world. Positive reinforcement, understanding, and inclusion in social activities can significantly enhance their quality of life and emotional health.

Management and Treatment of Enlarged Calves

How can families and health care providers can work together to reduce the burden of this symptom on their loved ones?

Current Approaches

While there is no cure for DMD, proactive symptom management can enhance quality of life and help children maintain greater independence despite physical limitations. Families of children with DMD often use the following resources to support muscle function and delay the loss of mobility:

• Physical therapy can help children build muscle strength, flexibility, and balance while relieving pain and discomfort from muscle contractures.
• Occupational therapy can help people navigate the world around them as independently as possible, including at home and at school.
• Orthotic devices, such as leg braces or splints, can help improve the amount of time someone with DMD can walk independently.
• Mobility aids, such as canes, walkers, and wheelchairs, can help people with mobility problems move around.
• Multispeciality care and multidisciplinary teams can address other systemic symptoms (conditions affecting the whole body) to reduce their impact on motor function.

A diverse team of health care providers is essential for managing DMD effectively. In addition to physical interventions, medications may be used to address symptoms like calf enlargement include the following:

• Corticosteroids may help delay joint, muscle, and lung decline in DMD.
• Eteplirsen (Exondys 51), an exon 51-skipping drug, helps increase the dystrophin protein, which is deficient in people with DMD due to a mutation (change) in the dystrophin gene.
• Golodirsen (Vyondys 53) and viltolarsen (Viltepso) — exon 53-skipping drugs — are beneficial for up to 8 percent of people with DMD.
• Delandistrogene moxeparvovec-rokl (Elevidys) is a gene therapy that aims to help strengthen muscles in people with DMD.

The choice of medication depends on the specific gene mutation, symptoms, and individual circumstances. Consult with your child’s medical team to explore available treatments and tailor a plan that best addresses their needs.

Ongoing Research and Future Directions

Researchers are continuing to look for potential treatments aimed at addressing the root causes of DMD. These include genetic approaches that would help to address symptoms, including calf enlargement. Caregivers of people with DMD are encouraged to keep up to date with new therapies for DMD, including on myDMDcenter.

By staying informed and actively participating in their child’s care, caregivers can make a profound difference in managing symptoms and improving quality of life.

Talk With Others Who Understand

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

Have you or a loved one been diagnosed with DMD? Did you notice calf enlargement before receiving a diagnosis? Share your experiences in the comments below.