Muscle Dystrophy Essay, Research Paper
DESCRIPTION OF MUSCULAR DYSTROPHY
Muscular dystrophy is a group of progressive, genetic diseases in which the muscles that control movement degenerate and weaken. In some forms of this inherited disease, the heart and other involuntary muscles and organs are affected too.
There are nine types of muscular dystrophy – (1) Myotonic Muscular Dystrophy (2) Duchenne Muscular Dystrophy (3) Becker Muscular Dystrophy (4) Limb-Girdle Muscular Dystrophy (5) Facioscapulohumeral Muscular Dystrophy (6) Congenital Muscular Dystrophy (7) Oculopharyngeal Muscular Dystrophy (8) Distal Muscular Dystrophy (9) Emery-Dreifuss Muscular Dystrophy.
The forms differ in age at which the disease appears, the severity, the muscles affected, the rate of symptom progression and the way the disease is inherited. Some forms only affect males, others affect both male and females. Some sufferers enjoy a normal life span with mild symptoms that progress very slowly while others experience fast and severe muscle weakness and wasting, and die in their late teens to early 20s. Through advances in medical care, children with muscular dystrophy are living longer than ever before.
There are several tests to determine whether one has muscular dystrophy or not, such as, a needle biopsy – a small sample of muscle tissue is taken from the thigh which is used to determine whether it contains dystrophin. Other tests include electromyography, electrocardiography, and the traditional “open muscle biopsy” where a cut is made into the skin and a piece of muscle is removed and the muscle fibers are examined under a microscope.
SYMPTOMS OF THE DISEASE
1. Myotonic (also called Steinert’s disease) – The most common form of muscular dystrophy in adults, myotonic muscular dystrophy affects both men and women, an it usually appears any time from early childhood to adulthood. In rare congenital cases, it appears in newborns. The name refers to a system myotomia – prolonged spasm or stiffening of muscles after use. This symptom is usually worse in cold temperatures. Myotonic dystropy results from a gene flaw on chromosome 19, one of the autosomes. The gene containing the defect is for an enzyme recently named myotonin protein kinase.
The disease causes muscle weakness and affect the central nervous system, heart, gastrointestinal tract, eyes (causing cataracts) and endocrine glands.
2. Duchenne – The most common form found in children, Duchenne muscular dystrophy affects only males. It appears between the ages of 2 and 6. Early signs of Duchenne include frequent falling, difficulty getting up from a sitting or lying position, and a waddling gait. Another hallmark is the apparent enlargement of the calf and sometimes other muscles, which is really due to an accumulation of fat and connective tissue in the muscle. A blood sample shows a very high level of creatine kinase, an enzyme that leaks out of damaged tissue. The muscles decrease in size and grow weaker over time yet may appear larger. Disease progression varies, but many sufferers need a wheelchair by age 12. In most case, the arms and the legs and spine becomes progressively deformed. Some sufferers are mildly retarded. The later stages of the disease are marked by severe breathing and heart problems. Sufferers usually die in their late teens or early 20s.
3. Becker – At one time, doctors thought that Becker dystrophy might be an entirely different disease from Duchenne. But after the gene for Duchenne was isolated, researchers found out that people with Becker dystrophy has defects in the same dystrophin gene and that the same dystrophin protein was affected as in Duchenne. The gene affects in Becker are different from those in Duchenne, so that some working dystrophin is made. It usually appears between the ages of 2 and 16 but can appear as late as age 25. Like Duchenne, it affects only males and causes heart problems. Disease severity varies. Sufferers can usually walk into their 30s and live further into adulthood.
4. Limb-girdle – This appears in the teens to early adulthood and affects males and females. In its most common form, it causes progressive weakness that begins in the hips and moves to the shoulders, arms and legs, Within 20 years, walking becomes difficult or impossible. Sufferers typically live to mid to late adulthood. Researchers found that gene defects on chromosomes 2,13,15 and 17 plays a role in the development of this type of muscular dystrophy.
5. Facioscaplohumeral – This appears from childhood to early teens and affects only males. It causes muscle weakness and wasting in the shoulders, upper arms and lower legs. Life threatening heart problems are common and can also affect carriers – those who have the genetic information for the disease but do not develop the full-blown version (including mothers and sisters of sufferers). Contractures occur early in the disease. Weakness can spread to chest and pelvic muscles. The disease progresses slowly and causes less severe muscle weakness than some other forms of muscular dystrophy.
6. Congenital – This is really a group of diseases, not a single disease. One form that has been clearly described is Fukuyama congenital dystrophy. This disorder involves severe weakness of the facial and limb muscles and a generalized lack of muscle tone, usually appearing before 9 months. Joint contractures are common. Brain abnormalities are also present, and most children have severe mental and speech problems. Seizures are often part of the disease, and medications are prescribed for these. Physical therapy is needed to minimize the contractures. The disease has been linked to a gene defect on chromosome 9, although the precise gene and its protein are so far unknown.
Another form of congenital dystrophy seems to be related to a deficiency or malfunction of the protein merosin, which normally lies outside muscle cells and links them to the surrounding tissue. The disorder is similarly to Fukuyama dystrophy, with muscle weakness evident at birth or in the first few months of life, severe and early contractures and often joint deformities. This disorder has been named congenital muscular dystrophy with merosin deficiency and appears to be due to an as-yet-unidentified defect on chromosome 6.
7. Oculopharyngeal – The name means eye and throat, muscular dystrophy. It usually starts with drooping of the eyelids, most often in the 40s or 50s. This is followed by other signs of eye and facial muscle weakness, as well as by difficulty in swallowing. The later stages of this slowly progressive disease may include weakness in the pelvic and shoulder muscles. Swallowing problems can lead to choking and recurrent pneumonia. The disease is linked to a gene defect on chromosome 14.
8. Distal – This is a group of rare muscle diseases, which have in common weakness and wasting of the distal muscles of the forearms, hands, lower legs and feet. In general, the distal dystrophies are less severe and progress more slowly and involve fewer muscles that the other dystrophies, although it can spread to other muscles.
9. Emery-Dreifuss – This is a very rare form of muscular dystrophy. Muscle weakness and wasting generally start in the shoulders, upper arms and lower legs. Weakness may later spread to involve the muscles of the chest and pelvic area. Contractures appear early in the disease, usually in the ankle and elbow. Potentially fatal heart problems are a common part of this disorder.
CURRENT METHODS AVAILABLE TO TREAT MUSCULAR DYSTROPHY
Although there is no cure for muscular dystrophy, there are several treatment options available to treat muscular dystrophy, depending on the type of muscular dystrophy. Physiotherapy is a common aid used to relieve discomforts of the disease. Spine surgery (scolosis and lordosis), assisted ventilation, drug treatment (steroids – clenbuterol), myoblast transfers and gene therapy are routes taken by muscular dystrophy patients depending on the form of the disease they have.
FUTURE DIRECTION FOR TREATMENT
Since the discoveries of the Duchenne muscular dystrophy gene and its protein (dystrophin), scientists have been working to develop safe and effective ways for inserting a working dystrophin gene into the muscles of boys with Duchenne and Becker muscle dystrophies.
As scientists identify the gene and protein abnormalities that cause other forms of muscular dystrophy, the promise of further genetic therapies is also expanding. Under the Muscular Dystrophy Association Advisory Committee, Association-funded scientists intensively search for non-genetic therapies – for example, corticosteroids – that might slow, stop or reverse the progression of the muscular dystrophies.