Definition:
Muscular dystrophy (MD) is a group of rare diseases.It refers to a group of genetic, hereditary muscle diseases that cause progressive muscle fiber weakness and break down. 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 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
There are many different types of muscular dystrophy (MD) – a group of conditions that progressively affect the muscles.Most are inherited and they vary in severity depending on type.There are no cures and no treatments to correct the loss of muscle cells that occur in MD.But a great deal can be done to help limit the effects.
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MD affects the skeletal or voluntary muscles that control movement in the arms, legs and trunk. It also can affect the heart and other involuntary muscles, such as those in the gut. MD passes from parent to child (genetic) and gets worse over time (progressive). There are nine major types of MD affecting people of all ages, from infancy to middle age or later. The two most common types of MD affect children: Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD, Both DMD and BMD affect boys almost exclusively, but in rare cases can also affect girls.
Causes:
Most are caused by mutations in genes involved in muscle structure and function.In some types of MD both the father and mother must have a faulty gene to pass it on, which is called recessive inheritance.In other types, it only needs one parent to pass on a faulty gene, which is called dominant inheritance.In one type, called Duchenne muscular dystrophy, the mother usually passes the faulty gene on to her son through the female sex chromosome, the X-chromosome.Sometimes the abnormal genes appear for the first time without having been passed down by either paren. Most type are caused byfaulty DNA
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. The dystrophin gene is the largest gene in humans.
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.
What may goe wrong?
These gene problems lead to damaged muscle cells that do not work properly.This may cause difficulty walking, clumsiness, frequent falls, difficulty standing and breathing problems.
However, the symptoms and their severity vary with the different types of MD.
Some of the different types of MD:
* Congenital MD – are a group of conditions in which symptoms are apparent at birth or within the first six months. The muscle weakness causes the baby to appear floppy.
* Duchenne MD – caused by an error in a gene called dystrophin and usually affects only boys, although there are rare cases in girls. It affects the muscles of the pelvis and thighs first, causing difficulty in walking between the ages of one and three.
* Becker MD – rarely affects people before the age of 10, and is considered a milder form than Duchenne MD. Again, it mainly affects boys.
* Emery-Dreifuss – typically starts in childhood or adolescence. The heart can also be affected.
* Facioscapulohumeral MD – affects facial (facio), shoulder (scapul) and upper arm (humeral) muscles, although the legs can sometimes be affected too.
* Oculopharyngeal MD – affects the eye (ocular) and throat (pharyngeal) muscles, with the first signs, such as droopy eyelids and difficulty swallowing, developing when the person is aged 50-60.
Who is affected?
Overall, about 1 in 2,000 babies born in the UK will have a neuromuscular disorder.
Duchenne MD is the commonest and most severe form. Around 100 boys are born with the condition in the UK each year .
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.
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.
There are treatments that can help alleviate symptoms, such as muscle spasm, and enable people with MD to lead a good quality of life.Exercise and physiotherapy helps to keep the muscles in good condition.Physical aids, such as braces or wheelchairs, can help the individual to maintain mobility.Couples who know that MD runs in their family can opt for genetic counselling.It is possible to test embryos while still in the womb to see whether they have inherited the genes responsible.Doctors can also test an embryo conceived using IVF to check that it does not carry any faulty gene before it is put into the mother’s womb
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.
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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.
Research Projects
A grid computing-based research project called “Help Cure Muscular Dystrophy” was launched on December 19, 2006 by Décrypthon. The Jain Foundation is involved in research into Miyoshi myopathy, a form of distal muscular dystrophy and LGMD2B, a limb-girdle muscular dystrophy.
Resources:
http://news.bbc.co.uk/2/hi/health/medical_notes/4250311.stm
http://en.wikipedia.org/wiki/Muscular_dystrophy
http://www.hnmrc.net/pd1989898396.html?categoryId=40
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