Muscular dystrophy – Wikipedia, the free encyclopedia

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 nameDuchenne 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] Duchenne and Becker muscular dystrophies, being caused by a mutation of a gene located on the X chromosome, predominantly affect males, although females can sometimes have severe symptoms as well. 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]

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; its helical nature allows it to act like a spring or shock absorber. Dystrophin links actin (cytoskeleton) and dystroglycans of the muscle cell plasma membrane, known as the sarcolemma (extracellular). In addition to mechanical stabilization, dystrophin also regulates calcium levels.[citation needed]

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.

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, standing frames and powered mobile arm supports) may be helpful. Inactivity (such as bed rest, sitting for long periods) and bodybuilding efforts to increase myofibrillar hypertrophy can worsen the disease.

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Muscular dystrophy - Wikipedia, the free encyclopedia