Muscular Dystrophy: What Causes This Disabling Condition?

What is muscular dystrophy? It's a group of inherited diseases known to cause progressive muscle degeneration. There is no known cure.

muscular dystrophy

Over time, people afflicted by muscular dystrophy experience atrophied and weakened muscles. The result: progressive degeneration of the skeletal muscles that control movement.

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We typically think of muscular dystrophy as a singular disease. But, per the National Institute of Neurological Disorders and Stroke, it’s more complex than that: “The muscular dystrophies (MD) are a group of more than 30 genetic diseases characterized by progressive weakness and degeneration of the skeletal muscles that control movement.”

Some forms of MD present early in life, while others present later. The rate of degeneration varies greatly, but most people with the affliction eventually become severely physically disabled.

What Causes Muscular Dystrophy?

The underlying cause of all muscular dystrophies is related to defects in the genetic code for dystrophin, a protein in skeletal muscle, heart muscle, and the brain. In most cases, it’s an inherited condition, but sometimes a new genetic mutation is implicated.

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Muscular Dystrophy Symptoms

Progressive muscle weakness is the predominant feature in MD. In most forms, it travels in a “proximal-to-distal” direction—that is, it starts in the chest, abdomen, hips, or shoulders and moves down the arms and the legs as the disease progresses.

Soft-tissue contractures occur when tissue becomes shortened, hard, and thick, restricting movement.

Spinal deformities can result from progressive muscle weakness and muscle imbalance. The most common is scoliosis (sideways curvature of the spine), which can lead to reduced lung capacity.

Progressive disability leads to problems walking. Many sufferers become wheelchair-bound, which can lead to other problems—worsening of contractures, loss of bone mass (osteopenia and osteoporosis) and rapidly progressive scoliosis.

Muscular dystrophy can be complicated by heart problems as well as lung problems. Heart muscle weakness along with reduced lung capacity can lead to cardiopulmonary failure.

Mild mental retardation is sometimes seen in children with muscular dystrophy, due to dystrophin abnormality in the brain. Also, seizures may develop in those with MD.

Types Of Muscular Dystrophy

There are more than 30 types of MD, each characterized by the clinical presentation and pathology. Forms include:

  • Duchenne Muscular Dystrophy: Sex-linked or X-linked, seen only in boys. There is one2 case per 3,500 live male births; ⅓rd of them, however, are spontaneous new mutations. Sufferers present in childhood with delayed walking, running and jumping, falls, difficulty sitting up, “waddling” gait, toe walking, large calf muscles (contractures), muscle pain and stiffness, and learning disability. Sadly, many sufferers die before the age of 30, usually due to heart or lung failure.
  • Becker Muscular Dystrophy: Sex-linked or X-linked, seen only in boys at a rate of one case per 30,000 live male births. Symptoms usually begin in the teenage years or 20s. It progresses slower than DMD.

Other, more rare types of muscular dystrophy include:

  • Emery-Dreifuss: Sex-linked.
  • Facioscapulohumeral: Autosomal dominant MDs (both parents are carriers). Presents in the teenage years or even as late as the 40s. Progression is slow and begins in the face and shoulders.
  • Myotonic MD or Steinert’s disease. Develops in adulthood, first affecting the face and neck causing the face to look long and thin, eyelids to droop eyelids and the neck becomes swan-like. The weakness is slowly progressive.
  • Limb-girdle MD: Autosomal recessive (one parent is a carrier). It affects hip and shoulder muscles first. Presents in childhood or the teenage years.

Diagnosis of Muscular Dystrophy

If you or your child have symptoms described above, make an appointment to see your doctor. He or she will take a medical and family history and perform a physical examination, including a full neurological examination.

According to the National Institute of Child Health and Human Development, diagnosis may include:

  • Blood tests, which involve general blood work plus creatine kinase (an enzyme raised in muscular dystrophy).
  • Electromyography is a test of the electrical activity in the muscle.
  • Genetic testing for genetic mutations.
  • Muscle biopsy involves analysis of a sample of muscle tissue that will help determine the form of muscle disease.
  • Exercise assessments are used to evaluate strength and respiratory function and to detect an increase in nitric oxide following exercise.
  • Electrocardiography and echocardiography will help diagnose and monitor heart involvement.
  • Lung function tests will help monitor respiratory involvement.
  • Ultrasonography is now replacing EMG for monitoring progression of MD. MRI is may also be used.

Treatment of Muscular Dystrophy

There is no cure or specific treatment for any of the MDs. Treatment focuses on slowing progression, reducing disability, and improving quality of life.

  • Therapies. Patients may benefit from physical therapy, respiratory therapy, speech therapy, occupational therapy and orthopedic appliances. Most sufferers will end up wheelchair bound. Assistive technology may help with communication and writing. Assistive ventilation may be needed if respiratory failure develops. If swallowing becomes an issue a feeding tube may need to be inserted.
  • Medication. Corticosteroids may help slow muscle degeneration. Anticonvulsants will help with seizures and any abnormal muscle activity. Immunosuppressants may help slow muscle degeneration.
    Antibiotics may be needed if respiratory or skin infections develop.
  • Creatine monohydrate supplementation is a new treatment undergoing research. Early studies have found that it increases muscle mass and contractions.
  • Surgery. Corrective orthopedic surgery may help relieve muscle contractures, deformities or scoliosis. A pacemaker may needed to be fitted if cardiac arrhythmias (irregular heartbeat) develops.
  • Gene therapies are being studied and are showing promise in animal studies.
  • Family screening. Families with a member afflicted by any form of MD are usually offered genetic screening and counseling.

Daily life

Quality of life may be improved for muscular dystrophy patients via the use of assistive technology, adapted automobiles, special clothing, home modification, lifts, wheelchairs, and service animals. Patients may need help with positioning to improve comfort and prevent bedsores and in transferring to and from chair, bed, car, and wheelchair. Adaptive beds and chairs can improve comfort and quality of sleep.

The Parent Project for Muscular Dystrophy offers excellent advice on additional services and advocacy groups.

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