MUSCULAR DYSTROPHY (MD)

Muscular dystrophy (MD) is a group of more than 30 inherited diseases. They all cause muscle weakness and muscle loss. Some forms of MD appear in infancy or childhood. Others may not appear until middle age or later. The different types can vary in whom they affect, which muscles they affect, and what the symptoms are. All forms of MD grow worse as the person's muscles get weaker. Most people with MD eventually lose the ability to walk.

There is no cure for muscular dystrophy. Treatments can help with the symptoms and prevent complications. They include physical and speech therapy, orthopedic devices, surgery, and medications. Some people with MD have mild cases that worsen slowly. Others cases are disabling and severe.

Types of muscular dystrophy

There are many different types of MD, each with somewhat different symptoms. Not all types of MD cause severe disability and many do not affect life expectancy.

Some of the more common types of MD include:

• Duchenne muscular dystrophy – one of the most common and severe forms, it usually affects boys in early childhood; men with the condition will usually only live into their 20s or 30s
• Myotonic dystrophy – a type of MD that can develop at any age; life expectancy is not always affected, but people with a severe form of it may have shortened lives
• Facioscapulohumeral muscular dystrophy – a type of MD that can develop in childhood or adulthood, it progresses slowly and is not usually life threatening
• Becker muscular dystrophy – closely related to Duchenne MD, but it develops later in childhood and is less severe; life expectancy is not usually affected so much
• Limb-girdle muscular dystrophy – a group of conditions that usually develop in late childhood or early adulthood; some variants can progress quickly and be life threatening, whereas others only develop slowly
• Oculopharyngeal muscular dystrophy – a type of MD that usually doesn't develop until a person is 50-60 years old and doesn't tend to affect life expectancy
• Emery-Dreifuss muscular dystrophy – a type of MD that develops in childhood or early adulthood; most people with this condition will live until at least middle age

Symptoms of Muscular Dystrophy

The symptoms of muscular dystrophy are the result of a deterioration of the body's muscles. This deterioration is due to the death of the muscle cells and muscle tissues and leads to ongoing muscle wasting and muscle weakness. Muscular dystrophy progresses and gets worse over time eventually. This results in difficulty walking, disability, the need for leg and hand braces, and ultimately the use of a wheelchair. 

The muscle weakness of muscular dystrophy often begins in the legs. This makes it difficult for a child to walk normally, and he or she may walk with their feet wide apart to help keep balance. The child may use his or her hands and arms to get up from the floor and assist with standing. There may be frequent falls, a waddling gait, limited range of motion and pain in the calves. By 12 years of age, a child is often completely unable to walk and must use a wheelchair. 

Diagnosis

The diagnosis of muscular dystrophy is based on the results of muscle biopsy, increased creatine phosphokinase (CpK3), electromyography, electrocardiography and DNA analysis.

A physical examination and the patient's medical history will help the doctor determine the type of muscular dystrophy. Specific muscle groups are affected by different types of muscular dystrophy.

Often, there is a loss of muscle mass (wasting), which may be hard to see because some types of muscular dystrophy cause a build up of fat and connective tissue that makes the muscle appear larger. This is called pseudohypertrophy.

Treatment

There's currently no cure for any form of muscular dystrophy. Research into gene therapy may eventually provide treatment to stop the progression of some types of muscular dystrophy. Current treatment is designed to help prevent or reduce deformities in the joints and the spine and to allow people with muscular dystrophy to remain mobile as long as possible.

Medications

Corticosteroids, such as prednisone, may help improve muscle strength and delay the progression of certain types of muscular dystrophy. But prolonged use of these types of drugs can weaken bones and increase fracture risk.

Therapy

Several different types of therapy and assistive devices can improve quality and sometimes length of life in people who have muscular dystrophy. Examples include:

Surgical remedies are an option for several of the problems common to muscular dystrophy, such as:

• Contractures. Tendon surgery can loosen joints drawn inward by contractures.
• Scoliosis. Surgery may also be needed to correct a sideways curvature of the spine that can make breathing more difficult.
• Heart problems. Some people who have heart problems related to muscular dystrophy may be helped by the insertion of a pacemaker, which prompts the heart to beat more regularly.

• Range-of-motion exercises. Muscular dystrophy can restrict the flexibility and mobility of joints. Limbs often draw inward and become fixed in that position. One goal of physical therapy is to provide regular range-of-motion exercises to keep joints as flexible as possible.
• Mobility aids. Braces can provide support for weakened muscles and help keep muscles and tendons stretched and flexible, slowing the progression of contractures. Other devices — such as canes, walkers and wheelchairs — can helfp maintain mobility and independence.
• Breathing assistance. As respiratory muscles weaken, a sleep apnea device may help improve oxygen delivery during the night. Some people with severe muscular dystrophy may need to rely on a ventilator — a machine that forces air in and out of their lungs.

Potential Treatment for Muscular Dystrophy Patients Through Stem Cell Therapy

While there is no cure to date for muscular dystrophy, stem cell research and implantation of healthy embryonic cells into individuals diagnosed with various forms of muscular dystrophy may improve function and mobility as well as slow the muscle-wasting process.

There are a number of different types of stem cells that scientists think may be used in different ways to develop treatments for muscular dystrophy. The main stem-cell-based approaches currently being investigated are:

1. Producing healthy muscle fibres: Scientists hope that if stem cells without the genetic defect that causes DMD can be delivered to patients’ muscles, they may generate working muscle fibres to replace the patient’s damaged ones.
2. Reducing inflammation: In muscular dystrophy damaged muscles become very inflamed. This inflammation speeds up muscle degeneration. Scientists believe certain types of stem cells may release chemicals that reduce inflammation, slowing the progress of the disease.

Beside stem cells, other therapeutic strategies such as gene therapy or small-molecule drugs for repairing the damaged gene are being tested in patients and in pre-clinical models. Future therapies are likely to use a combination of more than one of these approaches. Scientists are also studying the role of stem cells in the maintenance and repair of healthy muscles in order to understand in more detail what goes wrong in muscular dystrophy and how the problem could be corrected.

Research, clinical trials, therapies and treatments in stem cell implantation and transplants will continue in this field as researchers around the globe search for greater understanding of the best type of stem cells to be utilized in treating all forms of muscular dystrophy, offering hope to millions affected with the muscle wasting disease.