Muscular dystrophy is a group of conditions that damage and weaken your muscles over time.

This damage and weakness are due to the lack of a protein called dystrophin, which is necessary for typical muscle function. A deficiency of this protein can cause problems with walking, swallowing, and muscle coordination, among other symptoms.

Most diagnoses occur in childhood, although they can occur at any age.

Muscular dystrophies affect people of all sexes. However, the two most common types, Duchenne and Becker, are much more common in males. Combined, muscular dystrophies affect about 32 in 100,000 people in the United States , according to the Centers for Disease Control and Prevention (CDC).

的outlook for muscular dystrophy depends on the type of muscular dystrophy and the severity of symptoms.

的re’s no known cure for any of the muscular dystrophies, but there are treatments and therapies available. New drugs may help some people with a specific gene difference who live with Duchenne muscular dystrophy.

的re are several types of muscular dystrophy, which vary in symptoms and severity. Some are described below.

Duchenne muscular dystrophy (DMD)

Duchenne muscular dystrophy (DMD)is the most common among children. The majority of individuals affected are children assigned male at birth. It’s rare for children assigned female at birth to develop it.

的symptoms include:

  • trouble walking
  • 损失的反应
  • difficulty standing up
  • poor posture
  • bone thinning
  • scoliosis, an abnormal curvature of the spine
  • learning differences
  • breathing difficulties
  • swallowing problems
  • lung and heart weakness

People with DMD typically start using a wheelchairbefore their teenage years.

In the past, people lived with DMD into their late teens or 20s. However, it’s more common now for people tolive into their 30s. This is due in part to advances in medical treatment, including cardiac and respiratory care.

Combined, DMD and Becker muscular dystrophies affect about 14 in 100,000 U.S. males between the ages of 5 and 24 years.

Becker muscular dystrophy (BMD)

Becker muscular dystrophy (BMD) is similar to DMD, except it’s less severe. This type of muscular dystrophy is also more common in children assigned male at birth.

Muscle weaknessoccurs mostly in the arms and legs, with symptoms appearing between the ages of 11 and 25 years .

Other symptoms of BMD include:

Many with this condition won’t choose to use a wheelchair until they’re in their mid-30s or older, and a small percentage of people never require one. Most people with BMD live until middle age or later.

Congenital muscular dystrophy

Congenital muscular dystrophies are often apparent between birth and 2 years old. This is when parents begin to notice that their child’s motor functions and muscle control aren’t developing as they should.

Symptoms vary and may include:

  • muscle weakness
  • poor motor control
  • inability tositorstandwithout support
  • scoliosis
  • foot deformities
  • trouble swallowing
  • respiratory issues
  • vision problems
  • speech problems
  • learning differences

Symptoms range from mild to severe. The lifespan of someone with this type of muscular dystrophy also varies, depending on their symptoms. Some people with congenital muscular dystrophy pass away in infancy, while others live until adulthood .

About 1 in 100,000 people in the United States of all ages live with congenital muscular dystrophy.

Myotonic dystrophy

This form of muscular dystrophy causes myotonia, which is an inability to relax your muscles after they contract. Myotonic dystrophy is also called Steinert’s disease or dystrophia myotonica.

People with other types of muscular dystrophy don’t experience myotonia, but it’s a symptom of other muscle diseases.

Myotonic dystrophy can affect your:

Symptoms most often appear first in the face and neck. They include:

  • drooping muscles in the face, producing a thin, drawn look
  • difficulty lifting the neck due to weak neck muscles
  • difficulty swallowing
  • droopy eyelids, or ptosis
  • early baldnessin the front area of the scalp
  • poor vision, includingcataracts
  • weight loss
  • increased sweating

This dystrophy type may also causeimpotenceandtesticular atrophy. In others, it may causeirregular periodsandinfertility.

Myotonic dystrophy diagnoses are most likely to occur in adults in their 20s . The severity of symptoms can vary greatly. Some people experience mild symptoms, while others have potentially life threatening symptoms involving the heart and lungs. Many people with the condition live a long life.

About 8 in 100,000 people in the United States have myotonic dystrophy. It affects all sexes equally.

Facioscapulohumeral muscular dystrophy (FSHD)

Facioscapulohumeral muscular dystrophy (FSHD) affects the muscles in the face, shoulders, and upper arms. This type of muscular dystrophy is also known as Landouzy-Dejerine disease.

FSHD may cause:

A smaller number of people with FSHD may develop hearing and respiratory problems.

FSHD tends to progress slowly. Symptoms usually appear during teenage years , but they sometimes don’t appear until a person is in their 40s. Most people with this condition live a full life span.

About 4 in 100,000 people in the United States live with FSHD.

Limb-girdle muscular dystrophy (LGMD)

Limb-girdle muscular dystrophy (LGMD) refers to a group of more than 20 inherited conditions. They cause weakening of the muscles and a loss of muscle bulk. The symptoms usually begin in the shoulders and hips but may also occur in the legs and neck.

You may find it hard to get up out of a chair, use stairs, and carry heavy items if you have LGMD. You may also stumble and fall more easily.

Overall, about 2 in 100,000 people in the United States live with LGMD.

Many people with this form of muscular dystrophy experience severe disability within 20 years of the onset of the condition .

Oculopharyngeal muscular dystrophy (OPMD)

Oculopharyngeal muscular dystrophy (OPMD) causes weakness in your facial, neck, and shoulder muscles. Other symptoms include:

  • drooping eyelids
  • vision problems
  • trouble swallowing
  • voice changes
  • heart problems
  • difficulty walking

OPMD is one of the rarer types of muscular dystrophy, affecting fewer than 1 in 100,000 people in the United States . Individuals usually begin to experience symptoms in their 40s or 50s .

Distal muscular dystrophy

Distal muscular dystrophy is also called distal myopathy. It’s a group of over six diseases affecting the muscles furthest from the shoulders and hips, specifically the:

  • forearms
  • hands
  • calves
  • feet

的condition may also affect yourrespiratory systemand heart muscles. The symptoms tend to progress slowly and include a loss of fine motor skills and difficulty walking.

Most people develop symptoms of distal muscular dystrophy between the ages of 40 and 60 years old .

This condition is also particularly rare, affecting fewer than 1 in 100,000 people in the United States .

Emery-Dreifuss muscular dystrophy (EDMD)

Emery-Dreifuss muscular dystrophy (EDMD) usually begins in childhood and tends to affect more children assigned male at birth than children assigned female at birth. The symptoms include:

  • weakness in the upper arm and lower leg muscles
  • breathing problems
  • heart problems
  • shortening of the muscles in the spine, neck, ankles, knees, and elbows

Fewer than 1 in 100,000 people in the United States — of all ages — are affected by EDMD.

Most individuals with EDMD live until mid-adulthood. By 30 years old , nearly all have a heart issue that requires intervention, such as apacemaker. The most common causes of limited life expectancy are progressive heart or lung issues.

Differences in genes cause muscular dystrophy.

Thousands of genes are responsible for the proteins that determine muscle integrity. People carry genes on 23 pairs of chromosomes, with one-half of each pair inherited from a biological parent.

One of these pairs of chromosomes is sex-linked. This means the traits or conditions you inherit as a result of those genes may depend on your sex or the sex of your parent. The other 22 pairs aren’t sex-linked and are also known asautosomal chromosomes.

一个基因的改变可能导致缺陷的dystrophin, a critical protein. The body may not make enough dystrophin, may not make it the right way, or may not make it at all.

People develop muscular dystrophy in one of four ways. The gene differences that cause muscular dystrophy are normally inherited, but they can also come from a spontaneous mutation.

Autosomal dominant inherited disorder

A person inherits a gene difference from just one parent, on one of the 22 autosomal chromosomes.

Each child has a 50 percent chance of inheriting muscular dystrophy and people of all sexes are equally at risk. Because this is a dominant gene, only one parent needs to be a carrier for their child to develop muscular dystrophy.

Autosomal recessive inherited disorder

A person inherits a gene difference from both parents, on one of the 22 autosomal chromosomes. The parents are carriers of the gene but don’t develop muscular dystrophy themselves.

Children have a 50 percent chance of inheriting one copy of the gene and becoming carriers, and a 25 percent chance of inheriting both copies. All sexes carry the risk equally.

Sex-linked (X-linked) disorder

This inheritance is connected to the genes linked to the X chromosome.

Parents may carry two X chromosomes or an X and a Y chromosome. A child receives an X chromosome from one parent and either an X or a Y chromosome from the other. If a child receives a gene difference on the X chromosome from the parent with two X chromosomes, they’ll become carriers of the gene or develop muscular dystrophy.

A child with a faulty X chromosome develops muscular dystrophy if they also inherit a Y chromosome (as is typically the case with children assigned male at birth).

的y’re only carriers if they inherit an X chromosome from the other parent (as with children assigned female at birth). This other X chromosome offsets the effect of the X chromosome with the gene difference, as it can produce dystrophin.

Spontaneous mutation

In this case, muscular dystrophy develops because of a spontaneous change in genes. It occurs in people whose biological parents weren’t carriers of the gene difference.

Once the change occurs, the carrier can pass it on to their children.

Muscular dystrophies are genetic conditions. Afamily historyof muscular dystrophy is a risk factor for being a carrier or developing muscular dystrophy.

Because DMD and BMD are linked to the X chromosomes, children assigned male are much more likely to experience them.

However, even though children assigned female receive an X chromosome from each parent and should have adequate dystrophin production, they can still experience symptoms of DMD or BMD, such as muscle cramps, weakness, and heart issues.

Muscular dystrophy progresses a bit differently for every person. Complications also vary depending on the type of muscular dystrophy. Some of the more common complications affect:

  • movement
  • breathing
  • the heart
  • the spine

People with muscular dystrophy who become pregnant are also at a greater risk for certain complications during gestation and labor.

Mobility changes

Progressive muscle weakness can eventually limit mobility. Many people with muscular dystrophy will eventually use aids, such as a wheelchair. Specially designed wheelchairs can improve comfort, possibly reduce pain, and provide adequate muscle support.

Respiratory issues

Muscular dystrophy can cause breathing problems, as muscle weakness makes breathing harder. Trouble swallowing can lead toaspiration, or having substances in the airway or lungs. Overall, it’s harder for the respiratory system to do its job of bringing oxygen into the body and exhaling carbon dioxide.

Cardiac issues

的lack of dystrophin can also affect the heart, sinceit’s a muscle.

People with muscular dystrophy often havecardiomyopathy, or heart muscle disease. As part of ongoing muscular dystrophy treatment, doctors assess the state of your heart health and may recommend heart medication.

Contractures and scoliosis

Muscular dystrophy can also affect the skeletal muscles, which allow for flexibility in thetendonsand joints. The result is a pulling on tendons and joints into a flexed position, which can become permanent. This is called a contracture.

Weakness in the spinal muscles can cause curvature of the spine, or scoliosis.

Some contractures may be relieved with surgery. Corticosteroids and physical therapy may help prevent the onset of scoliosis.

Pregnancy considerations

People with muscular dystrophy may have to think differently about pregnancy, as it comes with risks and potential complications. Muscle weakness in the legs, hips, and abdominal muscles may make it hard to push during labor, increasing the chance ofcesarean deliveryor other intervention.

能来的广义肌肉无力myotonic dystrophy can lead to pregnancy loss. Pregnancy can also cause people with myotonic dystrophy to experience a faster onset of their condition and a worsening of their symptoms.

A number of tests can help your doctor diagnose muscular dystrophy. Your doctor can perform:

  • Blood testing.High levels of serum creatine kinase,serum aldolase, andmyoglobinmay all signal the need for further testing to confirm or rule out muscular dystrophy.
  • Genetic testing.High levels of creatine kinase and signs of insufficient dystrophin may indicate a need for genetic testing. This type of testing looks for a large mutation of the dystrophin (DMD) gene. If there’s no large mutation, the next set of genetic tests will look for small mutations.
  • Electromyography (EMG).EMGmeasures the muscle’s electrical activity using an electrode needle that enters your muscle. It can help doctors to distinguish muscular dystrophy from a nerve disorder.
  • Neurological physical exam.This exam rules out nervous system disorders and identifies the state of muscle strength and reflexes.
  • Cardiac testing.Cardiac testing identifies heart problems that sometimes occur with muscular dystrophy. Tests include anechocardiogramto look at the structure of the heart.
  • Imaging tests.MRIandultrasoundhelp doctors see the amount of muscle inside the body.
  • Exercise assessments.Exercise assessments look at muscle strength, breathing, and how exercise affects the body.

的re’s currently no cure for muscular dystrophy, but treatments can help manage your symptoms and slow the progression of the disease. Treatments depend on your symptoms and the kind of muscular dystrophy you have.

Medications

的Food and Drug Administration (FDA) has approved new treatments for some people with DMD. Many of these treatments use a new process called “exon skipping,” where the faulty segment (exon) of the dystrophin gene is patched over so the body can produce the protein.

的se new treatments include:

  • Eteplirsen(Exondys 51).Thisweekly injection为一个特定的突变dystrophin gene that is amenable to exon 51 skipping. According to the FDA’s 2016 approval notice, this applies to about 13 percent of people with DMD.
  • Golodirsen(Vyondys 53).This weekly injection is for people with a dystrophin gene difference amenable to exon 53 skipping. This applies to about 8 percent of people with DMD, according to the FDA’s 2019 approval notice.
  • Viltolarsen(Viltepso).This is also a weekly injection for those with a dystrophin gene difference that’s amenable to exon 53 skipping. The FDA approved viltolarsen (Viltepso) in 2020.
  • Casimersen (Amondys 45).This weekly injection is for those with a gene difference amenable to exon 45 skipping. This applies to about 8 percent of people with DMD, according to the FDA’s 2021 approval notice.
  • Deflazacort (Emflaza).This is acorticosteroidavailable in tablet and oral suspension forms. It’s approved for people ages 5 years and older with DMD.

Muscle therapy

Forms of muscle therapy have proven to be effective. These techniques involve working with a professional to improve physical function. Types of therapy include:

  • physical therapy, including physical activity and stretching, to keep muscles strong and flexible
  • respiratory therapy, to prevent or delay breathing problems
  • speech therapy, to conserve muscle strength throughspecific techniquessuch as slower speech, pausing between breaths, and using special equipment

Occupational therapy, a process that focuses on daily activities, can help those with muscular dystrophy:

  • become more independent
  • gain access to community services
  • improve coping skills
  • improve social skills

Other treatments

Other treatment options include:

  • corticosteroid drugs, which help strengthen muscles and slow muscle deterioration
  • assisted ventilationif respiratory muscles are affected
  • medication for cardiac problems
  • surgery to treat cardiac problems
  • surgery to help correct the shortening of muscles
  • surgery to repair cataracts
  • surgery to treat scoliosis

Symptoms, age of onset, and outlook depend on a person’s type of muscular dystrophy.

New researchis underway for a potential cure for DMD. In 2018, scientists found a way to repair a gene in canine models , ensuring adequate dystrophin production. They hope to one day use this advanced gene editing technique in people with DMD.

Breakthrough research such as this, and medications that slow the progression of DMD symptoms, offer new hope for many people with muscular dystrophy and their families.