Muscular Dystrophy

Muscular dystrophy is a group of more than 30 genetic diseases that cause muscles to become progressively weaker over time, making everyday activities increasingly difficult.

Table of contents

• What is Muscular Dystrophy?
• Types of Muscular Dystrophy
• Causes
• Symptoms
• How Muscular Dystrophy Affects Muscles
• Diagnosis
• Treatment
• Living with Muscular Dystrophy

What is Muscular Dystrophy?

Muscular dystrophy is a group of diseases that causes muscles to become weaker and lose mass over time^[1]. The condition is caused by changes in the genes that make proteins needed to form healthy muscles^[1]. These genetic conditions affect the functioning of your muscles, and in general, the symptoms worsen over time^[2].

Muscular dystrophy progressively weakens the muscles and eventually causes many people to lose the ability to walk^[3]. Some types of muscular dystrophy also affect the heart, lungs, gastrointestinal system, endocrine glands, spine, eyes, brain, or other organs^[3]. Over time, muscle weakness decreases mobility, making everyday tasks difficult^[4].

It is important to understand that muscular dystrophy is not contagious and cannot be caused by injury or activity^[3]. The disease is relatively rare, with all types combined affecting about 16 to 25 per 100,000 people in the United States^[2].

Types of Muscular Dystrophy

There are more than 30 types of muscular dystrophy^[1]. Each type affects specific muscle groups, appears at different ages, and varies in severity^[4]. Some types are present at birth or develop during childhood, while other forms develop during adulthood^[2].

Duchenne Muscular Dystrophy

This is the most common form of muscular dystrophy^[1]. Girls can carry the gene change that causes the disease, and some have symptoms, but this type is much more common in boys^[1]. Most often, the symptoms start in early childhood^[1]. As Duchenne muscular dystrophy (a type of muscular dystrophy that mainly affects boys) progresses, it affects the heart and lungs^[2].

The symptoms can include challenges with movement, such as late walking, frequent falls, trouble rising from the floor or from a lying or seated position, trouble running, jumping or climbing stairs, and waddling gait^[1]. Other symptoms can include large calf muscles, muscle pain and stiffness, learning or behavior-related challenges, and delayed growth^[1].

Becker Muscular Dystrophy

The symptoms of Becker muscular dystrophy are like those of Duchenne muscular dystrophy, but Becker is less severe^[1]. It is the second most common type and mainly affects boys, though girls can have milder symptoms^[2]. Symptoms can appear any time between the ages of 5 and 60, but they typically start by the teenage years^[2]. The severity varies from person to person^[2].

Myotonic Dystrophy

This is the most common type of muscular dystrophy diagnosed in adulthood^[2]. It affects men and women equally^[2]. People with myotonic dystrophy (a type affecting adults that makes it hard to relax muscles after use) have difficulty relaxing their muscles after using them^[2]. The condition can also affect the heart and lungs and may cause endocrine (hormone-related) issues, such as thyroid disease and diabetes^[2].

Congenital Muscular Dystrophies

Congenital muscular dystrophies refer to a group that become apparent at or near birth^[2]. They cause overall muscle weakness with possible joint stiffness or looseness^[2]. Depending on the type, congenital muscular dystrophies may also involve spinal curvature called scoliosis (sideways curving of the spine), breathing issues, intellectual disabilities, learning disabilities, eye issues, or seizures^[2].

Other Types

Other types include distal muscular dystrophy, which tends to affect people in their 40s and 60s and affects the muscles of the hands, feet, lower arms, and lower legs^[2]. Emery-Dreifuss muscular dystrophy mainly affects male children and young adults, causing muscle weakness in the shoulders, upper arms, and shins, and also affects the heart^[2]. Facioscapulohumeral muscular dystrophy most commonly affects muscles in the face, shoulders, and upper arms, with symptoms tending to appear before age 20^[2]. Limb-girdle muscular dystrophy affects the muscles in the upper arms, upper legs, shoulders, and hips and can affect people of all ages^[2]. Oculopharyngeal muscular dystrophy weakens muscles in the eyelids and throat, with symptoms often appearing in a person’s 40s or 50s^[2].

Causes

Muscular dystrophy is a genetic condition, which means it is caused by an altered gene^[6]. Different genes cause different types of muscular dystrophy^[6]. Many genes help to make the proteins that protect muscle fibers from damage^[7]. Muscular dystrophy occurs if one of these genes does not work properly^[7].

The altered gene can be passed on from your parents, or you can be born with it even if your parents do not have it^[6]. Some of these gene changes are inherited from a parent, while others are new changes that occur early in development, known as spontaneous or “de novo” gene changes^[7]. Spontaneous gene changes are not inherited, but they can be passed on to the next generation^[7].

Muscular dystrophy can run in families, or you can be the first in your family to have it^[4]. Sometimes people who have the same type of muscular dystrophy can have different gene changes^[5]. Even within the same type, people can have different symptoms^[5].

Symptoms

The main symptom of muscular dystrophy is muscle weakness that becomes worse over time^[1]. This makes everyday tasks harder to do^[1]. The type of muscular dystrophy that a person has determines the exact symptoms, the age range at which the symptoms start, and the muscle groups that are affected^[1].

Signs can include difficulty walking, difficulty lifting things, falling easily, muscle pain, and tightness in the joints^[6]. In young children, symptoms can include floppiness and taking longer than expected to crawl or walk^[6].

Some types of muscular dystrophy can also affect other parts of the body, such as the heart, lungs, or spine^[6]. Other health problems commonly associated with muscular dystrophy include heart problems, scoliosis, and obesity^[14]. Some people with muscular dystrophy may develop a swallowing disorder^[3].

How Muscular Dystrophy Affects Muscles

Muscles are made up of thousands of fibers^[3]. Each fiber contains cells surrounded by an outer layer, or membrane^[3]. Muscle fibers that make up individual muscles are bound together by connective tissue^[3].

The muscle fiber membrane contains a group of proteins, known as the dystrophin-glycoprotein complex (a set of proteins that protect muscles from damage), that prevent damage when muscle fibers contract and relax^[3]. When this protective membrane is damaged, muscle fibers begin to leak the protein creatine kinase and take on excess calcium^[3]. This damages the muscle fibers and eventually causes them to die, leading to progressive muscle degeneration^[3].

Some forms of muscular dystrophy are caused by defects in this dystrophin-glycoprotein complex^[3]. Others are caused by defects in the surrounding connective tissue^[3]. Still others are caused by expression of toxic gene products in muscle fibers^[3].

This damage can cause muscle degeneration, progressive weakness, fiber death and breakdown, fiber branching and splitting, and replacement of muscle tissue with fibrous tissue and fat^[3]. People with muscular dystrophy progressively lose muscle function, which can affect breathing^[3]. In many forms, the heart muscle also is affected, which can lead to cardiac failure^[3].

Diagnosis

To find out if you or your child has muscular dystrophy, your healthcare team asks about your or your child’s medical history, including general health and past illnesses^[8]. A physical exam is done^[8].

After that, the healthcare team might recommend tests based on the type of muscular dystrophy suspected^[8]. These may include:

• Blood and urine tests, including genetic tests and tests for certain enzymes that may be released by damaged muscles^[5]. Damaged muscles release proteins called enzymes into the blood, including creatine kinase^[8]. In a person who hasn’t had a serious injury, high blood levels of creatine kinase suggest a muscle disease^[8].
• Genetic testing, where blood samples can be checked for changes in some of the genes that cause types of muscular dystrophy^[8].
• Muscle biopsies, where a small piece of muscle can be removed through an incision or with a hollow needle^[8]. Then a lab checks this tissue sample and can tell muscular dystrophies apart from other muscle diseases^[8].
• Electromyography (a test that measures electrical activity in muscles), where a special needle is placed into the muscle to be tested^[8]. Electrical activity is measured as the muscle is relaxed and as it is gently tightened^[8]. Changes in the pattern of electrical activity can confirm a muscle disease^[8].
• Tests to monitor the heart, such as electrocardiography (a test that records the heart’s electrical activity) and echocardiogram (an ultrasound of the heart), which are used to check how well the heart works^[8].
• Tests to monitor the lungs, which are used to check lung function^[8].
• Imaging tests such as an MRI to look at muscle quality and bulk and measure fatty replacement of muscle tissue^[5].

If there’s a chance you could have a child with muscular dystrophy, a doctor may refer you to a genetic counselor to discuss the risks and options^[6]. Tests are available before, during, and after pregnancy for you and your baby^[6].

Treatment

There is currently no cure for muscular dystrophy, but treatment can help manage your symptoms^[6]. Medicines and other treatments can help manage the symptoms and slow the course of the disease^[1]. Treatment can help with the symptoms and prevent complications^[5].

You’ll normally be supported by a team of different specialists^[6]. Your treatment will depend on the type of muscular dystrophy you have and your symptoms^[6]. Treatment usually includes a combination of therapies, such as^[5]:

• Physical therapy to help keep muscles flexible and strong and to help with movement and relieve pain^[5][6].
• Occupational therapy to relearn lost motor skills and learn ways to work around weakened muscles^[5].
• Respiratory care, such as breathing exercises, oxygen therapy, and ventilators^[5].
• Speech therapy to help with speech and swallowing problems^[5].
• Assistive devices, such as wheelchairs, splints and braces, and walkers^[5].
• Medicines to help delay damage to muscles or minimize the symptoms, including steroids and other medicines for Duchenne muscular dystrophy^[5][6].
• Treatment for heart problems, such as a pacemaker or medicines like ACE inhibitors and beta blockers^[6].
• Surgery to treat some of the conditions associated with muscular dystrophy, such as heart problems, scoliosis, and cataracts^[5].

Living with Muscular Dystrophy

Muscular dystrophy is different for everyone^[6]. All types can affect your ability to move around^[6]. How severe your symptoms are and how quickly they get worse depends on the type you have^[6]. Many people with muscular dystrophy will need to use mobility equipment, such as a wheelchair, as the muscle weakness gets worse^[6].

A diagnosis of muscular dystrophy doesn’t mean you can’t go on to live a very full and rewarding life^[16]. Learning how muscular dystrophy can affect you and what solutions are available can help you live your best life while managing the disease^[16].

The level of disability caused by muscular dystrophy varies widely depending on which type a person has and when symptoms first appear^[16]. For some people, even everyday activities like brushing teeth or getting in and out of a car present a challenge, while for others, those types of activities and much more remain doable^[16].

Managing daily life may involve assistive devices to maintain mobility and independence^[21]. These aids should be used only in consultation with a trained occupational therapist or physiotherapist^[21]. Getting sufficient nutrition can be a challenge for people with muscular dystrophy, as many have difficulty chewing and swallowing, or feel fatigue at levels that reduce appetite and make eating a chore^[21].

The Centers for Disease Control and Prevention works to estimate the number of people with each kind of muscular dystrophy and funds research that collects critical information about the disease to improve care for those living with it^[4].