Muscular dystrophy
Classification and external resources
In affected muscle the tissue becomes disorganized and the concentration of dystrophin (green) is greatly reduced.
ICD-10	G71.0
ICD-9	359.0-359.1
MedlinePlus	001190
eMedicine	orthoped/418
MeSH	D009136

Muscular dystrophy (MD) is a group of muscle diseases that weaken the musculoskeletal system and hamper locomotion.^[1][2] Muscular dystrophies are characterized by progressive skeletal muscle weakness, defects in muscle proteins, and the death of muscle cells and tissue.^[3]

In the 1860s, descriptions of boys who grew progressively weaker, lost the ability to walk, and died at an early age became more prominent in medical journals. In the following decade, French neurologist Guillaume Duchenne gave a comprehensive account of thirteen boys with the most common and severe form of the disease, which now carries his name—Duchenne muscular dystrophy.

It soon became evident that the disease had more than one form. The other major forms are Becker, limb-girdle, congenital, facioscapulohumeral, myotonic, oculopharyngeal, distal, and Emery-Dreifuss muscular dystrophy.^[4] These diseases predominately affect males, although females may be carriers of the disease gene. Most types of MD are multi-system disorders with manifestations in body systems including the heart, gastrointestinal system, nervous system, endocrine glands, eyes and brain.^[4]

Apart from the nine major types of muscular dystrophy listed above, several MD-like conditions have also been identified. Normal intellectual, behavioral, bowel and sexual function is noticed in individuals with other forms of MD and MD-like conditions.^[5][6] MD-affected individuals with susceptible intellectual impairment are diagnosed through molecular characteristics but not through problems associated with disability.^[7] However, a third of patients who are severely affected with DMD may have cognitive impairment, behavioral, vision and speech problems.^[8][9]

Signs and symptoms[link]

• Progressive muscular wasting
• Poor balance
• Drooping eyelids
• Atrophy
• Scoliosis (curvature of the spine and the back)
• Inability to walk
• Frequent falls
• Waddling gait
• Calf deformation
• Limited range of movement
• Respiratory difficulty
• Joint contractures
• Cardiomyopathy
• Arrhythmias
• Muscle Spasms

Cause[link]

These conditions are generally inherited, and the different muscular dystrophies follow various inheritance patterns. However, mutations of the dystrophin gene and nutritional defects (with no genetics history) at the prenatal stage are also possible in about 33% of people affected by DMD.^[10] The main cause of the Duchenne and Becker types of muscular dystrophy is the muscle tissue's cytoskeletal impairment to properly create the functional protein dystrophin and dystrophin-associated protein complex.

Dystrophin protein is found in muscle fibre membrane, acting like a spring. It joins the membrane actin filaments. The protein is rod shaped around 150 nm in length, 3684 amino acids long, 427 kDa molecule weight. It is hydrophobic (repels water). Conformation is alpha-helical, allowing protein to act as a shock absorber, preventing overstress. Dystrophin links actin (cytoskeleton) and dystroglycans of the muscle cell plasma membrane, known as the sarcolemma (extracellular). Dystrophin functions in two ways; mechanical stabilisation and regulated calcium levels.

Diagnosis[link]

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.

Management[link]

There is no known cure for muscular dystrophy, although significant headway is being made with antisense oligonucleotides.^[11] Physical therapy, occupational therapy, orthotic intervention (e.g., ankle-foot orthosis), speech therapy and orthopedic instruments (e.g., wheelchairs and standing frames) may be helpful. Inactivity (such as bed rest, sitting for long periods) and bodybuilding efforts to increase myofibrillar hypertrophy can worsen the disease.

There is no specific treatment for any of the forms of muscular dystrophy. Physiotherapy, aerobic exercise, low intensity anabolic steroids, prednisone supplements may help to prevent contractures and maintain muscle tone. Orthoses (orthopedic appliances used for support) and corrective orthopedic surgery may be needed to improve the quality of life in some cases. The cardiac problems that occur with Emery-Dreifuss muscular dystrophy and myotonic muscular dystrophy may require a pacemaker. The myotonia (delayed relaxation of a muscle after a strong contraction) occurring in myotonic muscular dystrophy may be treated with medications such as quinine, phenytoin, or mexiletine, but no actual long term treatment has been found.

Occupational therapy assists the individual with MD in engaging in his/her activities of daily living (self-feeding, self-care activities, etc.) and leisure activities at the most independent level possible. This may be achieved with use of adaptive equipment or the use of energy conservation techniques. Occupational therapy may implement changes to a person's environment, both at home or work, to increase the individual's function and accessibility. Occupational therapists also address psychosocial changes and cognitive decline which may accompany MD, as well as provide support and education about the disease to the family and individual.^[12]

High dietary intake of lean meat, sea food, pulses, milk, egg, olive oil, leafy vegetables, bell pepper, fiber, wheat, antioxidants, fruits like blueberry, cherry etc. is advised. Decreased intake of carbohydrates, fats, dairy foods such as butter and milk, and caffeinated and alcoholic beverages is advised.^[13]

Diagnosis, neurology, GI-nutrition, respiratory care, cardiac care, orthopedics, psychosocial, rehabilitation, and oral care form the integral part of disease management, all through the patient's life span.

Prognosis[link]

The prognosis for people with muscular dystrophy varies according to the type and progression of the disorder. Some cases may be mild and progress very slowly over a normal lifespan, while others produce severe muscle weakness, functional disability, and loss of the ability to walk. Some children with muscular dystrophy die in infancy while others live into adulthood with only moderate disability. The muscles affected vary, but can be around the pelvis, shoulder, face or elsewhere. Muscular dystrophy can affect adults, but the more severe forms tend to occur in early childhood.

Types[link]

Research funding[link]

The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. Please improve this article and discuss the issue on the talk page. (December 2010)

Within the United States, the three primary federally funded organizations that focus on muscular dystrophy research (Gene therapy, Regenerative medicine) etc. include the National Institute of Neurological Disorders and Stroke (NINDS), National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and National Institute of Child Health and Human Development (NICHD).^[4]

In 1966, the Muscular Dystrophy Association began its annual Jerry Lewis MDA Telethon, which has arguably done more to raise awareness of muscular dystrophy than any other event or initiative. Disability rights advocates, however, have criticized the Jerry Lewis Telethon for portraying victims of the disease as deserving pity rather than respect.^[22]

On December 18, 2001 the MD CARE Act was signed into law and amends the Public Health Service Act to provide research for the various muscular dystrophies. This law also established the Muscular Dystrophy Coordinating Committee to help focus research efforts through a coherent research strategy.^[23][24]

See also[link]

• Muscular Dystrophy Association (USA)
• Muscular Dystrophy Campaign (UK)
• Muscular Dystrophy Canada (CAN)
• Muscle hypertrophy
• Myostatin

References[link]

External links[link]

• Muscular dystrophies at the Open Directory Project