What Is Muscular Dystrophy? Symptoms, Causes, Diagnosis, Treatment, and More
Muscular dystrophy is a group of more than 30 inherited conditions that cause progressive muscle weakness and loss. Some forms of muscular dystrophy are diagnosed in infancy or childhood, while the symptoms of others may not start until early or even late adulthood.
The different types of muscular dystrophy vary in terms of when symptoms start (in infancy, childhood, or adulthood), who they affect (men, women, or both), which muscles they affect, and what their symptoms are. But all forms of muscular dystrophy become increasingly worse or progress — meaning that your muscles get weaker the longer you live with the condition.
As a result, most people with muscular dystrophy eventually lose the ability to walk and must use a wheelchair to get around. Still, some people with the condition have mild cases that progress slowly, while others experience symptoms that quickly become severe and disabling.
At present, there’s no cure for muscular dystrophy, although certain treatments — including physical therapy, speech therapy, assistive orthopedic devices, surgery, and prescription medications — can help to slow progression, control some symptoms, and reduce the risk of complications. (1)
Each type of muscular dystrophy has some unique characteristics. The following are the major types of the disease. (2)
The most common and severe form of muscular dystrophy among children, primarily boys, is Duchenne muscular dystrophy (DMD). DMD accounts for more than half of all cases of muscular dystrophy among children, and it’s caused by lack of or dysfunction of dystrophin.
Dystrophin is a protein that helps strengthen muscle fibers and protect them from injury.
Children who have DMD usually experience initial weakness in their upper legs and pelvis. Symptoms include frequent falls, difficulty rising from a lying or sitting position, appearing to waddle when walking, having difficulty running or jumping, and having enlarged calf muscles from scar tissue buildup and replacement of muscle with fat tissue.
Symptoms of DMD typically appear between ages 3 and 5 and progress rapidly. Most children with DMD are unable to walk by age 12 and may eventually need a medical device to help breathe. (3)
Another form of muscular dystrophy caused by dystrophin deficiency is the Becker type. Becker muscular dystrophy has symptoms similar to those of DMD, but they tend to be milder and appear later in life — usually between ages 11 and 25, although they can also appear much later. Like DMD, Becker muscular dystrophy occurs primarily in boys and men.
Some people with Becker may never need to use a wheelchair, while others lose the ability to walk during their teens or later. (4)
Myotonic dystrophy is the most common adult form of the condition. In general, it causes an inability to relax the muscles following a contraction and can also cause swallowing difficulties, drooping eyelids, cataracts and other vision problems, baldness at the front of the scalp in men, weakness of the facial muscles, weight loss, increased sweating, fatigue, infertility, and impotence.
Myotonic dystrophy appears in one of two types, type 1 and type 2, abbreviated DM1 and DM2. Both are caused by abnormally expanded sections of DNA, but in different genes. Nonetheless, the mutations cause similar effects on the body.
Type 1 myotonic dystrophy is more common and usually more severe, although it can also appear in a “mild” form. Symptoms of both DM1 and DM2 usually start in a person’s twenties or thirties. (5,6,7)
Congenital muscular dystrophy is a rare form of the condition that typically begins to appear in children age 2 and younger. It affects both boys and girls, and those children who have it often require support to sit or stand and may never learn to walk.
Some children with congenital muscular dystrophy die in infancy, but others live into adulthood with only mild disability. Although there are more than 30 subtypes of congenital muscular dystrophy, roughly half of all cases in the United States are caused by a defect in or lack of the protein merosin, which surrounds muscle fibers.
This form is called merosin-deficient congenital muscular dystrophy, or MDC1A.
When congenital muscular dystrophy is caused by defects in other proteins, it may also affect the central nervous system.
Infants with this type of muscular dystrophy will have problems with motor function and muscle control that appear at birth or during infancy; develop chronic shortening of muscles or tendons around joints, called contractures, which prevent joints from moving freely; develop scoliosis (sideways curvature of the spine); have breathing and swallowing problems; have foot deformities; and have intellectual disabilities. (8)
Another type of muscular dystrophy is facioscapulohumeral dystrophy (FSHD). Facioscapulohumeral refers to the areas affected by this type: the face (facio), shoulders (scapulo), and upper arms (humeral).
The condition typically affects teens, although it may appear in adults up to age 40. It often appears first in the eyes and mouth.
People with FSHD may have difficulty opening and shutting their eyes or be unable to smile or pucker their lips. Other symptoms may include muscle wasting that causes the shoulders to appear slanted, impaired reflexes in the biceps and triceps, and difficulty swallowing, chewing, or speaking, as well as hearing loss.
The condition may also cause a curvature in the spine called lordosis. (9)
Limb-girdle muscular dystrophy affects both males and females, usually once they reach adolescence or young adulthood. Limb-girdle muscular dystrophy can progress quickly or slowly, but most people with the condition become severely disabled because of muscle damage and may be unable to walk within 20 years of being diagnosed.
Different types of limb-girdle muscular dystrophy are caused by different gene mutations, but in general, people with the condition inherit a defective copy of a gene from one parent, or, in the more severe form, two copies of the defective gene, one from each parent. People with either form first develop weakness around their hips.
This weakness usually spreads to the shoulders, legs, and neck. As a result, people with limb-girdle muscular dystrophy fall frequently and have difficulty getting up from chairs, climbing stairs, or carrying things.
They may also appear to waddle when they walk or have a rigid spine. (10)
Emery-Dreifuss muscular dystrophy can appear in childhood or adulthood and can progress quickly or slowly. It causes a combination of joint contractures, muscle weakness, and heart problems.
The contractures typically affect the elbows, joints of the neck, ankles, and heels, and the muscle weakness and atrophy usually start in the shoulders, upper arms, and calves.
One type of heart problem that is characteristic of Emery-Dreifuss muscular dystrophy is called a conduction block, in which the rhythm of the heartbeat is disrupted because the electrical impulses don’t communicate properly between the heart’s upper and lower chambers. A conduction block can lead to breathlessness, fainting, and even to sudden cardiac arrest. It can be treated with insertion of a pacemaker.
People with Emery-Dreifuss muscular dystrophy may also develop another type of heart problem called cardiomyopathy, a disease that makes it hard for the heart to pump blood to the rest of the body.
Emery-Dreifuss occurs most commonly in males, but girls and women who carry a genetic mutation that causes it may have heart conduction defects and muscle weakness. (11,12)
Distal muscular dystrophies refer to a group of diseases that affect the distal muscles — those of the forearms, hands, lower legs, and feet. They are caused by defects in a protein called dysferlin and can occur in both men and women, usually between ages 40 and 60.
Distal muscular dystrophy tends to be less severe and progresses more slowly than other forms of the condition, but it can spread to other muscles. People with this form of muscular dystrophy may be unable to move their hands and extend their fingers, and they have trouble walking and climbing stairs.
They may also develop breathing problems as the condition progresses and need a ventilator to maintain oxygen flow. (14)
Oculopharyngeal muscular dystrophy occurs in both men and women — usually in their forties or fifties — and is particularly common among Americans of French Canadian ancestry, individuals of Ashkenazi Jewish descent, and Hispanics from the Southwest region of the United States.
Oculopharyngeal muscular dystrophy can be mild or severe. It may cause drooping eyelids and other vision problems, swallowing problems, and muscle wasting and weakness in the neck, shoulders, and limbs. People with this form of muscular dystrophy may also develop heart problems and lose their ability to walk. (15)
The signs and symptoms of muscular dystrophy, and their severity, vary from one type of the disease to another and from one individual to another. And while the symptoms of all types of muscular dystrophy progress, or get worse, over time, the pace at which that happens also varies from type to type and person to person. It may also depend on the age at which a person is diagnosed and first receives treatment. For some types of muscular dystrophy, drug treatments can slow symptom progression somewhat.
While each person with muscular dystrophy is unique, some of the most common signs and symptoms of the disease include the following:
Some forms of muscular dystrophy, such as congenital muscular dystrophy, are also associated with learning disabilities, intellectual disabilities, and cognitive impairments.
In addition, Duchenne muscular dystrophy has been associated with lower verbal IQ, language delays, and deficits in working memory, attention, and executive function, among other problems. Some individuals with Duchenne are diagnosed with ADHD or autism because of these cognitive issues before it is recognized that they have a form of muscular dystrophy that accounts for their symptoms. But it’s important to note that such cognitive problems are not seen universally, and some people with Duchenne excel academically and in the workplace. (16)
Learn More About the Signs and Symptoms of Muscular Dystrophy
Learn More About the Signs and Symptoms of Duchenne Muscular Dystrophy
Muscular dystrophy is caused by genetic variations that interfere with the production of proteins needed to build and maintain healthy muscles.
The most common forms of muscular dystrophy are caused by a variation on the X chromosome influencing production of a protein called dystrophin, while other types of muscular dystrophy have their own set of unique genetic variations, affecting the production of other proteins.
But even within one type of muscular dystrophy, different individuals may have different genetic variations, leading to similar, but not identical, symptoms.
In most cases, the genetic variations that cause muscular dystrophy run in families and are passed from parents to children. However, for some types of muscular dystrophy, you have to inherit two copies of a nonworking gene, one from each parent, to have the disease; this is called an autosomal recessive inherited disorder. (The word “autosomal” means the gene in question is located on one of the autosomes, the numbered pairs of chromosomes that don’t affect a person’s sex.)
For other types of muscular dystrophy, you need only inherit one copy of a nonworking gene from one parent to have the disease; this is called a dominant inherited disorder.
A third type of genetic inheritance is called a sex-linked, or x-linked, disorder, in which the genetic variation is carried on the X chromosome. Because males have only one X chromosome, they’re more likely to have X-linked forms of muscular dystrophy than females, who have two X chromosomes. That’s because in females, the normal copy of the X chromosome can usually compensate for the one that has the variation.
It’s also possible for spontaneous gene variations — in which genes change for no apparent reason, regardless of parental DNA — to cause muscular dystrophy. Such variations occur during development in the embryo. This means the condition can develop in people with no family history of it.
Given the complexity of how muscular dystrophy can be inherited, couples who want to have children and who know or suspect they carry gene variations that cause muscular dystrophy are generally advised by their physician to meet with a genetic counselor before they conceive to better understand the risk of their offspring having the disease and discuss ways of lowering that risk.
The diagnosis of any type of muscular dystrophy usually begins with your doctor taking a patient history — including asking about any family history of the condition — and performing a physical examination. During the exam, your doctor will look for any abnormal curvature in your spine, abnormalities in the way you walk, or evidence of muscle wasting, weakness, or diminished reflexes.
Your doctor may also order a blood test to check your creatine kinase (CK) level. CK is an enzyme that leaks out of damaged muscle. When elevated CK is found in blood, it typically means muscle is breaking down due to muscular dystrophy or inflammation.
A very elevated CK level indicates that the muscles themselves are the likely cause of the weakness, although it doesn’t identify the type of muscle disorder you may have.
Because muscular dystrophy is a genetic disorder, your doctor will likely recommend you undergo genetic testing to determine whether there are any genetic variations — particularly if your blood tests reveal an elevated CK level. The type of variations involved will depend on what type, if any, of muscular dystrophy you have.
Finally, your doctor may also suggest a muscle biopsy, which involves the surgical removal of a small sample of muscle. The muscle tissue can be examined under microscope for the presence and appearance of specific proteins, and it can also be used to extract DNA for genetic testing.
In addition to blood and genetic tests, your doctor may also perform neurological tests to rule out nervous system disorders that could cause similar symptoms.
Heart tests, like an electrocardiogram (ECG), may also be used to measure the rate and frequency of heartbeats. Some forms of muscular dystrophy cause heart problems, such as an irregular heartbeat or cardiomyopathy.
Finally, imaging tests like MRI or ultrasound imaging may be used to examine muscle quality and bulk, as well as the fatty replacement of muscle tissue. This can help spot muscle wasting and other possible symptoms of muscular dystrophy.
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Learn More About How Duchenne Muscular Dystrophy Is Diagnosed
The life expectancy, or life span, for people with muscular dystrophy depends on the type involved, and when it’s diagnosed.
Children, for example, who develop DMD usually die in their late teens or early twenties from heart trouble, respiratory complications, or infections, although new ventilator technologies and improved drug treatments for these ailments have extended the lives of many people with this form of muscular dystrophy.
Life expectancy for people with myotonic dystrophy varies considerably. Many people have a normal life expectancy, but those with more severe congenital forms — from birth — may die while still a newborn or only survive for a few years. In addition, people with myotonic dystrophy can develop heart problems that may lead to death in their thirties or forties.
Finally, individuals with facioscapulohumeral dystrophy, limb-girdle, Emery-Dreifuss, distal, and oculopharyngeal dystrophies may have a normal life span. But symptoms can vary from mild to severely disabling, affecting mobility and other necessary functions — like eyesight and hearing — later in life.
There’s no cure for muscular dystrophy, and no treatment can reverse the damage it causes to muscles. But there are therapies and medications that can address some of the problems associated with the symptoms and help control the symptoms themselves.
These therapies can also help you maintain your quality of life and ability to perform day-to-day tasks.
Some examples of therapies that may be helpful are:
Physical Therapy Working with a physical therapist can help you keep muscles flexible and strong. A physical therapist may also recommend a combination of light muscle-building and stretching exercises to help you maintain strength and flexibility.
Speech Therapy Some forms of muscular dystrophy cause weakness in the facial and throat muscles, affecting speech or swallowing. Speech therapists can teach people how to work around these problems or, if needed, use special communication equipment.
Occupational Therapy As your physical abilities change, an occupational therapist can teach you techniques to conserve your energy while performing daily tasks or how to find alternative ways of accomplishing what you wish to do. An occupational therapist can also teach you how to use assistive devices such as wheelchairs and utensils, if needed.
Drug Treatment Prescription medications that can help slow or control the symptoms of the condition include the following:
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Learn More About Treatment Options for Duchenne Muscular Dystrophy
Learn More About the Doctors and Specialists Who Treat Muscular Dystrophy
Complications are generally understood to be indirect, or sometimes long-term, consequences of having a condition, although they may also overlap with symptoms in some cases. These are some of the health complications associated with muscular dystrophy:
Contractures Contractures are the shortening of muscles or tendons around the joints, and they can limit mobility beyond that caused by muscle weakness. Regular stretching and range-of-motion exercises can delay contractures, but if they become severe, your doctor may recommend surgery, which may restore some joint function and reduce discomfort.
Breathing Difficulties As it progresses, muscular dystrophy may affect the muscles associated with breathing. As a result, an individual with muscular dystrophy may need to use a breathing device (a ventilator), perhaps initially only at night but possibly also during the day. Sleep apnea, in which a person repeatedly stops breathing during sleep, is a common respiratory problem in people with muscular dystrophy.
Coughing Difficulties Weakened respiratory muscles interfere with a person’s ability to cough, and inadequate coughing allows mucus secretions to accumulate in the lungs, raising the risk of infection. Some people with muscular dystrophy need to use a cough assist device or manual assistance to clear secretions.
Swallowing Difficulties Progressive muscle weakness may negatively affect the ability to swallow when eating or drinking. Some of the potential consequences of swallowing difficulties include nutrient deficiencies and a condition called aspiration pneumonia, in which food or mouth secretions can get trapped in the lungs, leading to pneumonia, a lung infection.
In some cases, a speech-language pathologist can help you relearn how to swallow. Alternatively, your doctor may recommend the use of a feeding tube to ensure proper nutrition.
Heart Disease The heart muscles may be affected by muscular dystrophy as the condition progresses. One common heart complication in people with muscular dystrophy is called cardiomyopathy. As the name indicates, cardiomyopathy is a heart muscle disease, and it can cause heart failure. The condition is treatable. Your doctor may recommend blood pressure medications and other drugs to help you maintain adequate heart function.
Women who carry a genetic mutation that causes DMD are at a higher-than-normal risk of developing fibrosis, or scarring, of the heart muscles at a relatively young age. The condition leads to deterioration of heart function.
Scoliosis Spinal deformities are common in some forms of muscular dystrophy. The most frequent spinal complication associated with the condition is scoliosis, or curvature of the spine to one side or the other. It typically occurs in people who can no longer stand or walk and who use a wheelchair full-time.
Osteoporosis Another orthopedic complication linked with muscular dystrophy is osteoporosis, a condition in which the bones become fragile because of a loss of mass. While osteoporosis is normally associated with older age, in people with muscular dystrophy, it may develop as a result of treatment with corticosteroids, particularly in those with DMD.
People with osteoporosis are at increased risk for bone fractures — an important consideration given that weakness in the legs from muscular dystrophy may make a person more prone to falling.
The U.S. Centers for Disease Control and Prevention (CDC) estimates that 1 in every 5,000 American males between ages 5 and 9 has either DMD or Becker muscular dystrophy, the two most common forms of the condition.
The prevalence of these conditions among Black Americans was lower than the prevalence among white Americans, and the risk was higher among Hispanic Americans than whites. (17)
In all, muscular dystrophies are estimated to affect 250,000 individuals in the United States.
In general, although the number of children born with DMD has remained relatively stable — at approximately 17 per 10,000 live male births in the United States in 2019 — for years, the prevalence of the condition has increased. (18)
This is because improvements in the diagnosis and treatment of muscular dystrophy mean those with the condition are living longer.
Currently available treatments typically focus on managing the symptoms of muscular dystrophy and slowing its progression. But ongoing research is focused on finding a cure for the condition.
For example, researchers have been experimenting with gene-replacement therapy strategies in DMD and limb-girdle muscular dystrophy for several years. These approaches involve removing the genetic mutations that cause disruptions in the production of dystrophin and replacing them with healthy genes. (19)
Another approach being evaluated involves boosting the genes involved in the production of utrophin, a protein similar to dystrophin that is not affected by the same genetic mutations.
Gene modification therapy offers another option. In one approach that is currently in clinical trials, researchers are working with drugs that boost the body’s production of functional dystrophin.
To date, these drugs appear to be effective in 15 percent of people with DMD.
Finally, studies are underway looking at approaches for reversing the muscle deterioration caused by muscular dystrophy, either with medication or by injecting stem cells.
All these potential treatments are currently in clinical trials and likely several years from becoming available. But you or your child may be eligible to enroll in one of these studies.
Learn More About Duchenne Muscular Dystrophy in Girls and Women
In April 2020, a group of specialists in neuromuscular disease published recommendations on managing muscular dystrophy conditions amid the COVID-19 pandemic. At the time, there was no information available on how the pandemic, and the changes in healthcare delivery caused by it, had affected the muscular dystrophy community. The writers noted that people with muscular dystrophy were at higher risk of complications from COVID-19 infections, particularly if they were taking steroids or had underlying respiratory or cardiac dysfunction.
While many of the pandemic’s most acute risks have since ebbed, COVID-19 does pose an ongoing concern for anyone managing a muscular dystrophy condition. To stay on top of these risks and the ongoing guidelines, the Parent Project Muscular Dystrophy organization created an online COVID-19 information center, with links to the latest recommendations as well as many other resources.
The Muscular Dystrophy Association has similarly created a COVID-19 Resources page that includes a link to a survey and to information on the organization’s advocacy response to the pandemic.
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