Overview of Muscular Dystrophy

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Muscular dystrophy (MD) represents a group of nine inherited muscle disorders that involve a combination of muscle weakness and muscle wasting, though some types of the disease also present with other characteristics. MD can begin in infancy or childhood, or later in life. Diagnosis typically begins with the evaluation of one's symptoms but is only confirmed after significant testing. While there is no known cure for muscular dystrophy, treatments may help slow progression and improve symptoms.

Though MD is considered rare, it has become a household name largely due to Muscular Dystrophy Association's Labor Day Telethon, which was hosted for many years by Jerry Lewis and ran from 1966 to 2015.

Types

The nine subtypes of MD can influence what parts of the body are affected, to what extent, and how quickly. They are:

  • Duchenne muscular dystrophy: Duchenne muscular dystrophy (DMD) is the most common childhood form of muscular dystrophy, with symptoms typically beginning between ages 2 to 6. It mostly affects boys, though girls may be mildly affected. DMD affects approximately 1 in every 3,500 live male births (about 20,000 new cases each year), and it impacts children of all ethnic backgrounds.
  • Becker muscular dystrophy: This form is similar to DMD, but it begins later and progresses more slowly.
  • Myotonic muscular dystrophy: Also known as Steinert's disease or MMD, this is the most common form of adult muscular dystrophy. It starts with muscle weakness in the face and then moves on to the feet and hands. A woman with myotonic MD can give birth to an infant with a congenital form of the disease.
  • Congenital muscular dystrophy: Congenital muscular dystrophy represents a group of muscular dystrophies that are present at birth. This form of MD can affect both boys and girls.
  • Limb-girdle muscular dystrophy: Limb-girdle muscular dystrophy begins in the teen or early adult years of both genders and starts in the hips.
  • Facioscapulohumeral muscular dystrophy: Facioscapulohumeral muscular dystrophy (FSH MD) begins in adolescence or early adulthood and affects both genders. FSH MD primarily affects the muscles of the face, shoulder blades, and upper arms.
  • Oculopharyngeal muscular dystrophy: Oculopharyngeal muscular dystrophy generally begins in the fourth or fifth decade of life and affects the eyes and throat.
  • Distal muscular dystrophy: Distal muscular dystrophy includes a number of muscle diseases which begin in adulthood and mainly affect the limbs.
  • Emery-Dreifuss muscular dystrophy: Emery-Dreifuss muscular dystrophy is a less common form of childhood MD that only affects boys. Weakness is less severe than with DMD.

Symptoms

Progressive muscle weakness is the characteristic symptom of all types of muscular dystrophy, though the muscles affected can vary depending on a person's age, the type of MD, and how long he or she has had the disease.

Generally speaking, the signs and symptoms of muscular dystrophy typically begin between early childhood and the teen years, but may begin in early adulthood in some forms of the disease, such as facioscapulohumeral MD.

Sometimes, young children with muscular dystrophy may appear to have a delay in the development of motor skills or may miss certain milestones because of such deficiencies.

While muscle weakness is the main effect of the condition, the most prominent symptoms appear when a person tries to use several weight-bearing muscles at once. Muscle weakness generally involves the large muscles of the trunk, rather than the small muscles of the fingers or toes. This is why the symptoms might not be obvious in the early stages.

Early symptoms can include:

  • Falling
  • Waddling when walking
  • Difficulty getting from a sitting to a standing position
  • Toe walking

Later symptoms can include:

  • Shortness of breath
  • Muscle stiffness
  • Choking when swallowing

The imperfect muscle structure of muscular dystrophy causes weakness, and over time, leads to muscle atrophy (loss of muscle). Often, fat cells replace the muscle, which makes the muscles appear normal or even large in size, despite the fact that they are truly smaller than normal. 

Muscular Dystrophy Signs and Symptoms

Causes

Muscular dystrophy is caused by a lack of certain proteins that are needed for muscle structure and function. Specifically, many of the types of MD are caused by a lack of or a defect in dystrophin, a protein that helps optimize muscle function. 

Most types of muscular dystrophy are X-linked hereditary diseases, which means they are more common in boys, who inherit the disease from their mothers.

Women have two X chromosomes, either of which may carry the disease. If one of a woman's chromosomes codes for normal muscle protein production, though the other does not, she may not have any symptoms of MD at all (the same goes for her daughter). However, since all boys inherit the X of their XY chromosome pairing from their mothers, they will manifest the disease if the X they inherit is defective.

Researchers have discovered more than 30 genes responsible for causing different types of MD, and genetic testing can assess relevant gene variants and evaluate whether women with a family history of certain forms of the disease are carriers.

Causes and Risk Factors of Muscular Dystrophy

Diagnosis

DMD, in particular, is usually based on the development of the symptoms in the child’s preschool years. Parents or teachers begin to notice the boy having difficulty climbing stairs or keeping up with other children.

The National Institute of Health (NIH) lists several tests a healthcare provider may use to diagnose MD and determine the type. Those tests include:

  • Blood tests: These are used to measure specific enzymes related to the breakdown of muscle fibers and sugar. For example, a blood test for creatine kinase (CK or CPK) may show elevated levels that are 10 to 100 times higher than normal. This test indicates that muscle damage is occurring but does not confirm the diagnosis.
  • Muscle biopsies may be performed so that muscle tissue can be examined under a microscope.
  • Neurological tests can help rule out the presence of other neurological disorders. Additionally, neurological testing can evaluate muscle weakness, reflexes, coordination, and more.
  • Cardiac tests may be used to gather information about whether or not there is impairment in heart function, which can be a complication of MD.
  • Exercise assessments may be performed to check a person’s strength, respiratory function, and the levels of certain chemicals (like nitric oxide) after exercise has taken place.
  • Imaging, such as MRI and ultrasounds, might be used to take pictures and gather insights about the quality and density of muscle tissue. 
    How Muscular Dystrophy Is Diagnosed

    Treatment

    Treatments for muscular dystrophy are aimed at keeping people strong and mobile for a long as possible, and managing other conditions that may develop as a result of a weakening musculoskeletal system.

    Medications

    Medications like steroids and other immunosuppressant drugs may be used to slow the progression of the disease, improve energy, and lessen the symptoms, but they can have serious side effects when taken for a long time. Anticonvulsant medications may be used to reduce seizures and diminish muscle spasms.

    If there’s an overlapping condition present, such as a heart issue or an infection, a healthcare provider may prescribe heart medications or antibiotics. Furthermore, for people who’ve been diagnosed with DMD, the Food and Drug Administration (FDA) has approved Eteplirsen, or Exondys 51, a drug specifically indicated to treat patients who have a genetic variant leading to a dystrophin protein deficiency.

    Therapy

    Physical, occupational, speech, and respiratory therapies can be instrumental in helping people maintain their range of motion, mobility, activities of daily living, speech and communication, swallowing, and lung function. Additionally, some therapists can recommend assistive devices such as braces, canes, walkers, and wheelchairs to support weakened muscles.

    Surgery  

    The NIH reports patients with MD may need to undergo surgery to correct a variety of issues. The types of surgeries can include an insertion of a pacemaker when heart problems are present, surgery to improve spinal alignment when a curvature of the spine (scoliosis) interferes with breathing, and surgery to remove cataracts from the eyes and improve vision. In cases of DMD, some patients may need to have a tracheostomy tube surgically placed in their trachea (windpipe) due to the severity of breathing problems, and some may require a respirator. 

    How Muscular Dystrophy Is Treated

    A Word From Verywell

    Receiving a diagnosis of MD can be incredibly overwhelming. Although there’s currently no cure for MD, the medical community has made great strides in understanding the illness and improving the life expectancy and quality of life of those living with it. Whether you or a loved one have been diagnosed with MD (or you just want to learn more about it), arm yourself with as much information as possible so that you can make decisions that are right for you and your family’s healthcare.

    Muscular Dystrophy: Signs, Symptoms, and Complications
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