When your child shows signs of muscle weakness or struggles with everyday movements, it can be an emotional and confusing time. You want to understand what’s going on, and you want answers. Two conditions that might come up during the diagnosis process are myotonic dystrophy and muscular dystrophy.

Although myotonic dystrophy is a specific type of muscular dystrophy, these conditions differ in how they affect the body, how they progress, and what they mean for your child’s future. Understanding these differences can help you make informed decisions about your child’s care and well-being.

What Are Myotonic Dystrophy and Muscular Dystrophy?

Myotonic dystrophy is a specific form of muscular dystrophy, which means it belongs to the larger group of conditions called muscular dystrophy. However, it has its own unique features.

One of the key differences is a symptom called myotonia. This is when your muscles can’t relax easily after contracting (tightening). For example, someone with myotonia may grip an object and struggle to release it. In addition to myotonia, myotonic dystrophy causes gradual muscle weakness that worsens over time.

Muscular dystrophy is a broader group of more than 30 genetic conditions. These conditions all lead to muscles becoming weaker as they break down over time. Unlike myotonic dystrophy, most types of muscular dystrophy don’t cause myotonia.

Who Do These Conditions Affect?

Myotonic dystrophy can affect people of all ages, from newborns to adults. In its most severe form, called congenital myotonic dystrophy, babies may be born with weak muscles and have delays in reaching developmental milestones, such as sitting or walking. For some people, symptoms might not show up until they are teenagers or adults. Unlike most types of muscular dystrophy, myotonic dystrophy affects men and women equally, according to the NHS.

Muscular dystrophy often begins in early childhood, with some types primarily affecting boys, according to Mayo Clinic. For example, Duchenne muscular dystrophy (DMD), the most common form, usually appears between ages 1 and 3. DMD causes noticeable delays in walking, climbing stairs, or running. Other forms, like limb-girdle muscular dystrophy (LGMD), can affect men and women, according to the National Institute of Neurological Disorders and Stroke. Symptoms may appear later in childhood or even adulthood.

What Are the Types of Myotonic and Muscular Dystrophy?

There are two main types of myotonic dystrophy: myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2).

Myotonic dystrophy type 1 — also known as Steinert disease — can be severe and sometimes appears at birth. It may include symptoms like myotonia and systemic (bodywide) issues such as eye or heart problems.

Myotonic dystrophy type 2 is a milder form that’s usually diagnosed in adulthood. DM2 symptoms may include muscle weakness and myotonia. It generally progresses more slowly and is considered less severe than DM1.

Muscular dystrophy includes several distinct types, each with unique symptoms and progression. Common types seen in children are:

• DMD
• LGMD
• Becker muscular dystrophy (BMD)
• Congenital muscular dystrophy (CMD)
• Facioscapulohumeral muscular dystrophy (FSHD)
• Emery-Dreifuss muscular dystrophy (EDMD)

What Causes Myotonic and Muscular Dystrophy?

Myotonic dystrophy, including DM1 and DM2, is caused by genetic mutations (changes to a gene’s DNA sequence) that can be passed down from parent to child. In DM1, the severity of symptoms and the age at which they appear often depend on the number of repeated DNA sequences in the gene. These repeats can grow larger in later generations, which may make the condition worse or appear earlier — a process referred to as anticipation. Inheriting just one mutated gene from either parent is enough to develop myotonic dystrophy.

Muscular dystrophy is also caused by genetic mutations, which weaken muscles by affecting essential proteins needed for muscle function. How muscular dystrophy is inherited depends on its type. For example, DMD and BMD are X-linked recessive, meaning the faulty gene is on the X chromosome and primarily affects males. Other types, such as LGMD, can be inherited in different patterns, including autosomal dominant (requiring one faulty gene) or autosomal recessive (requiring two faulty genes, one from each parent).

What Are the Signs and Symptoms of Myotonic and Muscular Dystrophy?

The most distinctive symptom of myotonic dystrophy is myotonia, where muscles become stiff and take longer to relax after movement. People with myotonic dystrophy may also experience weakness in facial muscles, along with difficulty swallowing and chewing.

Myotonic dystrophy affects multiple systems. It might cause a person’s eyes to develop cataracts (cloudy area in the eye’s lens). It could cause arrhythmias (irregular heart rhythms) and breathing problems. It might even affect the endocrine system, causing a variety of other symptoms, including insulin resistance. In some cases, it can also lead to cognitive challenges, such as difficulties with memory, learning, or focus.

In DM1, symptoms of muscle weakness usually begin in the distal muscles (those in the hands and lower legs). In contrast, DM2 primarily affects the proximal muscles (muscles in the hips and shoulders). In DM2, the weakness progressively worsens over time. The severity and progression vary widely among individuals, with DM1 often being more severe than DM2.

Generally, symptoms of muscular dystrophy include progressive muscle wasting and loss of strength. These can show as gait issues (problems with walking, running, movement) and difficulty performing daily tasks. However, muscle weakness usually begins in different muscle groups depending on the specific type.

For example, in DMD, weakness typically starts in the proximal muscles and progresses rapidly, eventually affecting mobility and daily activities. In distal muscular dystrophy, weakness starts in the distal muscles and progresses more slowly.

The symptoms of muscular dystrophy also progress differently depending upon the type. In later stages, some muscular dystrophies can affect the lungs (causing breathing problems) and the heart. This is especially common in DMD and BMD.

Certain types, such as Duchenne, can also lead to scoliosis (curved spine) and contractures (stiffened muscles or tendons), which limit movement.

How Are They Diagnosed?

To diagnose myotonic dystrophy, doctors start by looking at symptoms. These may include muscle weakness, myotonia, and other issues such as cataracts, heart rhythm problems, or difficulty swallowing.

They may also ask about family history, since myotonic dystrophy is often inherited. The most important test for myotonic dystrophy is genetic testing, which looks for changes in specific genes (DMPK or CNBP). Sometimes, a test called electromyography (EMG) is used to check how muscles respond to electrical signals.

To diagnose muscular dystrophy, healthcare providers start by checking for muscle weakness, especially in areas like the shoulders, hips, or thighs. Doctors may then perform several tests to determine the specific type of muscular dystrophy:

• Blood test — They may order a blood test to look for high levels of creatine kinase, an enzyme released when muscles are damaged.
• Genetic testing — Genetic testing is used to confirm the type of muscular dystrophy by identifying changes in the genes responsible for the condition (e.g., dystrophin gene for DMD).
• Muscle biopsy — In some cases, a muscle biopsy may be done, where a small piece of muscle tissue is examined under a microscope for signs of muscle disease.
• Organ function tests — Additional tests, like heart and lung function tests, might be needed if these organs are affected by the disease.

How Are They Treated?

Currently, there’s no cure for myotonic dystrophy or muscular dystrophy. However, early intervention can help manage symptoms and slow the progression of the disease.

For myotonic dystrophy, common treatments include:

• Muscle relaxants to help reduce myotonia and muscle stiffness
• Physical therapy and occupational therapy to improve mobility and maintain muscle function
• Speech-language therapy to address slurred speech and swallowing difficulties
• Cardiac monitoring and pacemakers for individuals with arrhythmias
• Cataract surgery to correct vision problems
• Diabetes management (e.g., insulin therapy) for those with insulin resistance

For muscular dystrophy, treatments include:

• Corticosteroids to slow muscle degeneration in some types, such as DMD
• Physical therapy to maintain muscle strength and flexibility
• Mobility aids and assistive devices, such as wheelchairs, walkers, or braces, to improve movement and prevent falls
• Cardiac care and respiratory support, including ventilation assistance, as the disease progresses

Connect With Others Who Understand

On myMDteam — the social network for people living with muscular dystrophy and their loved ones — members share their experiences, ask questions, and find support from others who understand the challenges of living with muscular dystrophy.

Have you or a loved one struggled to understand a muscular dystrophy diagnosis? What questions do you still have? Share your thoughts or experiences in the comments below, or start a conversation by posting on your Activities page.