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Muscular Dystrophy (MD)

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Introduction

Muscular Dystrophy (MD) is a genetic disorder caused by a defective gene, this hereditary disease is characterized by progressive muscle weakness, which prevents the movement of muscles. It causes weakening & breaking down of muscle fibers. The muscles become weak & susceptible to damage. This disease affects the voluntary or skeletal muscles, which control the movements of legs, arms, & trunk. It can also affect the heart muscles & other involuntary muscles, such as muscles in the gut. Some forms of MD are found in infancy or childhood, others may only appear until middle age. This progressive disease is more common in boys than girls.

Each type of MD is caused by a genetic mutation. A genetic deficiency of muscle protein, namely dystrophin. This also responsible for the most common types of MD.

Types

 There are nine major types of muscular dystrophy according to:

  • The age that the symptoms appear,
  • Location of muscles involved,
  • The manner in which the defective gene is passed on, & the rate that symptoms progress.

All these types affect people of all age groups.

The most common types of MD that affect children result from a genetic deficiency of the muscle protein & Dystrophin.

They include:

  • Becker Muscular Dystrophy (BMD)
  • Duchenne Muscular Dystrophy (DMD)

Other common types of MD are:

  • Congenital muscular dystrophy
  • Myotonic muscular dystrophy
  • Facioscapulohumeral muscular dystrophy
  • Limb-girdle muscular dystrophy
  • Distal muscular dystrophy
  • Emery-Dreifuss muscular dystrophy

Signs & Symptoms

The signs and symptoms of MD vary according to the types of MD. Each type of MD is different in the body part affected, age of onset, & progression of the disease. Some of the common symptoms are muscle weakness, apparent lack of coordination, obesity, progressive muscle wasting, weakness & loss of function, joint contractures, frontal baldness, cataracts, drooping eyelids, mental impairment, and gonadal atrophy.

Becker muscular dystrophy: affects mainly boys. Its symptoms are less severe and may start later. People with BMD show the symptoms such as muscle breakdown and weakness and some problems related to breathing, heart, bones, and joints. The onset of symptoms is at the age of 11.

Duchenne's muscular dystrophy: This is the most severe type of MD that affects children. Symptoms of DMD are frequent fall, large calf muscles, weakness in lower leg muscles, causing difficulty in jumping & running, difficulty in getting up from a sitting or a lying position, wadding gait, & mild mental retardation. The symptoms appear between the ages 2 & 6. This type of MD first affects the upper arms, upper legs, & pelvis.

Myotonic dystrophy: Causes weakness and stiffness of muscles, weakening of voluntary muscles that control legs and arms, weakening of muscles of face, head, and neck, and fainting, or dizziness.

Facioscapulohumeral MD: Causes progressive muscle weakness involving the muscles of face, shoulders, abdomen, upper arms, feet, pelvic area, and lower arms.

Oculopharyngeal MD: Causes drooping of the eyelids, weakness of eye muscles, and muscles of face and throat. It results in difficulty in swallowing.

Diagnosis

A careful review of patient's family history of muscle disease can help the doctor for an accurate diagnosis. In addition to physical examination and family history, the doctor prescribes some tests for the diagnosis of the condition. A blood test such as determination of serum creatine kinase (CK) is useful to diagnose MD because this enzyme is released by the damaged muscles. High levels of CK indicate a muscle disease such as muscular dystrophy. Other helpful tests are electromyography, ultrasonography, muscle biopsy, and genetic testing.

Treatment

There is no cure for any type of muscular dystrophy, treatment is given to slow the progress of the disease, it is designed to reduce or prevent the deformities in the spine & joints.

Various treatment options include medications such as mexiletine, baclofen, carbamazepine, & anti-inflammatory corticosteroids in order to manage muscle weakness, spasms, & stiffness, as well as improve muscle strength, physical therapy, assistive devices, and surgery. Physical therapy focuses on providing regular range-of-motion exercises to delay the progression of contractures and keep the joints flexible.

Some assistive devices such as braces, walkers, canes, & wheelchairs help maintain the mobility & independence. A tendon release surgery is advised in order to release the contractures.

Disclaimer: This article is for informative purposes only, and should not be used as a replacement for expert medical advice.

References

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https://en.wikipedia.org/wiki/Muscular_dystrophy

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