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The Muscular Dystrophies are a group of genetic diseases characterized by progressive weakness and degeneration of the skeletal muscles that control movement.

There are many forms of Muscular Dystrophy, some noticeable at birth (congenital muscular dystrophy), others in adolescence (Becker Muscular Dystrophy), but the 3 most common types are Duchenne, Facioscapulohumeral, and Myotonic. These three types differ in terms of pattern of inheritance, age of onset, rate of progression, and distribution of weakness.

What is Muscular Dystrophy?

Duchenne Muscular Dystrophy (also known as Pseudohypertrophic Muscular Dystrophy or Muscular Dystrophy - Duchenne type) is an inherited disorder characterized by rapidly progressive muscle weakness that starts in the legs and pelvis and later affects the whole body. It is the most common form of muscular dystrophy, and usually affects only boys, but in rare cases it can also affect girls. It is an X-linked recessive inherited disease.

What are the causes of Duchenne Muscular Dystrophy?

One third of the cases are known to be caused by the development of spontaneous mutations in the dystrophin gene, while the remainder is inherited. Boys with Deuchenne Muscular Dystrophy develop weak muscles because the muscle fibers that were present at birth are destroyed. It is due to mutations in the Dystrophin gene, which encodes a cell membrane protein in myocytes (muscle cells).

Dystrophin is required inside muscle cells for structural support it strengthens muscle cells by anchoring elements of the internal cytoskeleton to the surface membrane. Without it, the cell membrane becomes permeable, so that extracellular components enter the cell, increasing the internal pressure until the muscle cell “explodes” and dies. The subsequent immune response can add to the damage.

What are the Symptoms?

1. Muscle weakness.
2. Rapidly progressive.
3. Frequent falls.
4. Difficulty with motor skills (running, hopping, jumping).
5. Progressive difficulty walking.
6. Ability to will be lost by age 11.
7. Fatigue.
8. Intellectual impairment (in approximately 30% of Duchenne’s patients).
9. Skeletal deformities.
10. Chest and back (scoliosis).
11. Muscle deformities.
12. Contractures of heels, legs.
13. Pseudohypertrophy of tongue and calf muscles.
14. Mild mental retardation in some cases.

Is there any treatment?

There is no specific treatment for Duchenne Muscular Dystrophy. Treatment is aimed at control of symptoms to maximize the quality of life. Physical activity is encouraged. Inactivity (such as bed rest) can worsen the muscle disease. Cardiac abnormalities may require a pacemaker. Corticosteroids such as prednisone can slow the rate of muscle deterioration but causes side effect.

Physiotherapy

Physiotherapists are concerned with enabling children to reach their maximum physical potential. Their aim is to:

- Minimize the development of contractures and deformity by developing a programmed of stretches and exercises where appropriate
-Anticipate and minimise other secondary complications of a physical nature
-Prescribe equipment such as orthoses, callipers, wheelchairs and standing frames
-Advise on moving and handling issues and equipment
-Monitor respiratory function and advise on techniques to assist with breathing exercises and methods of clearing secretions.

Mechanical Ventilator Assistance: Volume Ventilators

Modern “volume ventilators,” which deliver a preset volume (amount) of air to the child with each breath, are valuable in the treatment of children with muscular dystrophy related respiratory problem.

What is the Prognosis?

The prognosis of Muscular Dystrophy varies according to the type of Muscular Dystrophy and the progression of the disorder. Some cases may be mild and progress very slowly over a normal lifespan, while other cases may have more marked progression of muscle weakness, functional disability, and loss of the ability to walk. In Duchenne Muscular Dystrophy, death usually occurs in the early 20s.

What Research is being Done to Cure Duchenne Muscular Dystrophy?

Anti sense therapy with the use of Anti sense oligonucleotides (AON) has the potential to restore effectively the production of dystrophin, the defective protein, in >70% of Duchenne Muscular Dystrophy. This could result in increased life expectancy through improved muscle survival and function.

Recent scientific research has demonstrated the potential of this technique to skip mutated dystrophin exons, restore the reading frame and generate functional dystrophin protein. Having demonstrated proof-of-principle in human cell culture and animal model studies, efficacy and safety is yet to be determined in human clinical trials.

In some patients with Duchenne Muscular Dystrophy, the disease is caused by a nonsense mutation (premature stop codon) in the gene that makes the dystrophin protein. PTC124 has been shown to partially restore dystrophin production in animals with Deuchenne Muscular Dystrophy due to a nonsense mutation. The main purpose of this study is to understand whether PTC124 can safely increase functional dystrophin protein in the muscles of patients with Duchenne Muscular Dystrophy due to a nonsense mutation.

Doctors in Italy have treated mice with the most common form of Muscular Dystrophy by correcting the defective gene responsible for the disease.

The technique uses RNA with a genetic code complementary to that of the defective gene.

What are the Preventive Measures?

Genetic counseling is advised if there is a family history of the disorder. Duchenne muscular dystrophy can be detected with about 95% accuracy by genetic studies performed during pregnancy.

Filed under Duchenne Muscular Dystrophy, Health