muscular dystrophy reference

Muscular dystrophy refers to a group of genetic, hereditary muscle diseases that cause progressive muscle weakness.[1][2] Muscular dystrophies are characterized by progressive skeletal muscle weakness, defects in muscle proteins, and the death of muscle cells and tissue. Nine diseases including Duchenne, Becker, limb girdle, congenital, facioscapulohumeral, myotonic, oculopharyngeal, distal, and Emery-Dreifuss are always classified as muscular dystrophy[4] but there are more than 100 diseases in total with similarities to muscular dystrophy. Most types of MD are multi-system disorders with manifestations in body systems including the heart, gastrointestinal and nervous systems, endocrine glands, skin, eyes and other organs.

History

The first historical account of muscular dystrophy appeared in 1830, when Sir Charles Bell wrote an essay about an illness that caused progressive weakness in boys. Six years later, another scientist reported on two brothers who developed generalized weakness, muscle damage, and replacement of damaged muscle tissue with fat and connective tissue. At that time the symptoms were thought to be signs of tuberculosis.[citation needed]

In the 1850s, 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 13 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, and that these diseases affected people of either sex and of all ages.[citation needed]

[edit] Genetic cause

These conditions are inherited, and the different muscular dystrophies follow various inheritance patterns. The best-known type, Duchenne muscular dystrophy (DMD), is inherited in an X-linked recessive pattern, meaning that the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes, and is thus considered sex-linked. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation must generally be present in both copies of the gene to cause the disorder (relatively rare exceptions, manifesting carriers, do occur due to dosage compensation/X-inactivation). Males are therefore affected by X-linked recessive disorders much more often than females. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons. In about two thirds of DMD cases, an affected male inherits the mutation from a mother who carries one altered copy of the DMD gene. The other one third of cases probably result from new mutations in the gene. Females who carry one copy of a DMD mutation may have some signs and symptoms related to the condition (such as muscle weakness and cramping), but these are typically milder than the signs and symptoms seen in affected males. Duchenne muscular dystrophy and Becker's muscular dystrophy are caused by mutations of the gene for the dystrophin protein and lead to an overabundance of the enzyme creatine kinase.[5][6] The dystrophin gene is the largest gene in humans.[7]

[edit] Symptoms

Principal symptoms include:

* Progressive Muscular Wasting (weakness)
* Poor Balance
* Frequent Falls
* Walking Difficulty
* Waddling Gait
* Calf Pain
* Limited Range of Movement
* Muscle Contractures
* Respiratory Difficulty
* Drooping Eyelids (ptosis)
* Gonadal Atrophy
* Scoliosis (curvature of the spine)
* Inability to walk

Some types of Muscular Dystrophy can affect the heart, causing cardiomyopathy or arrhythmias.

[edit] Diagnosis

The diagnosis of muscular dystrophy is based on the results of a muscle biopsy. In some cases, a DNA blood test may be all that is needed.

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.

[edit] Prognosis

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.

[edit] Treatment

There is no known cure for muscular dystrophy. Inactivity (such as bed-rest and even sitting for long periods) can worsen the disease. Physical therapy, Occupational therapy, speech therapy and orthopedic instruments (e.g., wheelchairs, standing frames) may be helpful.

There is no specific treatment for any of the forms of muscular dystrophy. Physical therapy to prevent contractures (a condition when an individual with a muscular dystrophy grows and the muscles don't move with the bones and can easily be slowed down and/or make the individual's body straighter by daily physical therapy), 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 adapted equipment or the utilization of energy conservation techniques. Occupational therapy may also 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