Muscular Dystrophy


Muscular Dystrophy Essay, Research Paper


There is no single disease called muscular dystrophy. Muscular Dystrophy (MD) refers to a group of inherited diseases that are characterized by progressive weakness and degeneration of muscle tissue, with or without the breakdown of nerve tissue. (Emery, A.) The muscular dystrophies are a group of muscles diseases that have three features in common: they are hereditary; they are progressive; and like stated above, each causes a characteristic of selective pattern of weakness.

The muscles of the heart and some other involuntary muscles are also affected in some forms of MD, and a few forms involve organs as well. There are many types of muscular dystrophy, but in each type, there is an eventual loss of strength, increasing disability, and sometimes deformity. One major form of muscular dystrophy is Duchenne, and that will be discussed.

* Description of Duchenne Muscular Dystrophy *

Duchenne muscular dystrophy (DMD) is the most common childhood form of muscular dystrophy and occurs in approximately one in every five thousand boys born. Although Duchenne muscular dystrophy is an inherited disease, and present from the initial stages of fetal development, there is no indication at birth that the baby is anything less than normal. It is rare for any delay in development to be noticed in the first year of life. (Nowak, R.)

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* Symptoms *

Early signs of Duchenne occur between the ages of two and six which 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. This enlargement is a sign of muscle disease rather than an indication of good strength. Muscle wasting is initially limited to the shoulder and pelvic areas. Within several years, Duchenne muscular dystrophy affects the muscles of the upper trunk and arms. Eventually, all the major muscles are affected. (Nowak, R.)

Problems are usually not evident until eighteen months to four years of age. On average, a diagnosis is not made until the child is five, although with increasing awareness of the problem, some boys are diagnosed earlier. At least half of affected boys do not walk until eighteen months of age or later. In retrospect, almost all parents have noted that their children never walked or ran normally.

Over the first few years of life, these children have difficulty climbing and getting up from the floor. Like I said before about these children falling, parents often comment on how frequently this happens. Walking up on the toes is common. The boys are not able to keep up with their friends in physical

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activities at kindergarten or school and they are often regarded as clumsy or lazy.

Parents may be falsely encouraged by a seeming improvement between the ages of three and seven, but this may be due to natural growth and development. Weakness progresses rapidly after age eight or nine, resulting in the inability to walk or stand alone. Leg braces may make walking possible for a year or two, but by early adolescence, walking becomes impossible. (Touchette, N.)

In the late stages of Duchenne muscular dystrophy, there is a noticeable shortening of muscles and the loss of muscle tissue. This may result in the inability to move the major joints of the body. There may also be a noticeable increase in the curvature of the spine. Lung capacity may decrease, resulting in an increased susceptibility to respiratory infections. The function of the lungs in people with DMD depends mostly on the strength of the muscles, which move the chest in breathing and coughing. This usually determines the length of life for affected people, provided that the other complications do not occur. (Touchette, N.)

When the muscles involved in breathing become very weak, lung function becomes inadequate so that there is not enough oxygen and too much carbon dioxide in the blood. This causes drowsiness, headaches, and a general lack of well being. When

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this happens, assistance with breathing through a facemask, used during sleep, may return the blood oxygen and carbon dioxide levels to normal and relieve the symptoms.

These are often successfully treated with antibiotics and respiratory therapy. Severe respiratory and heart problems mark the disease?s final stages, usually in the boy?s teens or early twenty?s. (Emery, A.) Mild mental retardation has been noted in some (by no means all) boys with Duchenne dystrophy.

* Cause *

Scientists discovered exactly which piece of genetic material is missing in Duchenne muscular dystrophy patients. They were then able to work out which protein in the body this genetic material makes. The protein is called dystrophin. Boys who have Duchenne muscular dystrophy do not have the genetic material that gives the message to the body to make dystrophin. Without dystrophin, Duchenne muscular dystrophy occurs.

Dystrophin is a large protein, which is found on the inner side of the membrane surrounding each muscle fiber. It seems to be important in maintaining the shape and structure of the muscle fiber. If dystrophin is missing, the muscle fiber breaks down and is unable to work properly. (Emery, M.) Further research has shown that dystrophin is attached to other proteins at the edge of muscle fibers and that probably helps anchor the fibers to connective tissue surrounding them.

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Normally, muscle fibers can be replaced by regeneration. During the first few years, muscle fibers that break down in boys with Duchenne muscular dystrophy are being replaced, but the body has only a limit to continue replacing muscle fiber. Eventually the rate of regeneration cannot keep up with the rate of degeneration. As a result, there is a reduction in the number of good muscle fibers and the whole muscle becomes weaker. (Anderson, B.)

Duchenne muscular dystrophy is a rare neuromuscular disorder that is inherited as an X-linked recessive trait. The gene that is responsible for this disorder has been identified on the short arm of the X-chromosomes. Symptoms develop due to the lack of the protein dystrophin in the muscles. Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother. X-linked recessive disorders are conditions that are coded on the X-chromosome. Females have two X-chromosomes, but males have one X-chromosome and one Y-chromosome.

Therefore, in females, the normal gene on the other X-chromosome can mask disease traits on the X chromosome. Since males only have one X-chromosome, if they inherit a gene for a disease present on the X, it will be expressed. Men with X-linked disorders transmit the gene to all their daughters, who

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are carriers, but never to their sons. Women who are carriers of an X-linked disorder have a fifty-percent risk of transmitting the carrier condition to their daughters, and a fifty-percent risk of transmitting the disease to their sons. (See attachment)

Approximately thirty percent of patients with Duchenne muscular dystrophy have no family history of the disorder. This can mean that the genetic mutation is new in those families. The disorder is diagnosed by finding a deficiency of dystrophin in the muscles. (Nowak, R.)

?Only males are affected, with rare exceptions.

?Unless a boy with DMD is known to be at risk because of his family history, he is unlikely to be diagnosed before the age of two or three years.

?Most boys with DMD walk alone at a later age than

average, and then in unusual manner. They may frequently

fall, have difficulty rising from the ground, or

difficulty going up steps.

?Sometimes there is intellectual handicap, which, although rare in boys, is more frequent than in other children. There is an effect on posture and gait?the way the boy stands, walks and runs?especially up hills or steps.

?Calf muscles and sometimes other muscles look very well developed or excessively large, while other muscles are poorly developed.

?The usual typical style of walking is sometimes described as waddling.

?Whether standing still or walking, the boy usually has an exaggeration of the forward curve of the lower part of the back, sometimes called swayback. The medical term for this is lordosis.

?Later development is a tendency to stand and walk on the forward part of the foot with the heels off the ground.

?Female relatives of affected males may be carriers.

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?The mothers of affected males, in families with more than one affected male, are carriers.

?The mothers of affected males with no affected relatives are not always carriers because their sons may have been affected by new mutations.

?The son of a carrier has a fifty-percent probability of being affected.

?The daughter of a carrier has a fifty-percent probability of being a carrier.

?The sons of an affected male are all unaffected; his daughters are all carriers.

* Test *

Creatine kinase (CK) test is an enzyme (protein) that is important for energy production within muscle fibers. (Emery, A.) If a disease process such as muscular dystrophy damages a muscle fiber, some of the CK leaks out into the blood. Normally there is only a small amount in the blood, but in Duchenne muscular dystrophy, there may be ten to one hundred times the normal amount. (Emery, A)

There are very few other disease processes which cause such a high level of CK in the blood. Progression varies somewhat from child to child. The use of orthopedic devices and physical therapy can prolong the ability to walk. Frequently, however, a wheelchair will be needed by age twelve.

When muscles contract (shorten), and there is electricity

flowing through the muscle tissue, this is known as electromyography (EMG). (Touchette, N.) An abnormal muscle has an abnormal pattern of electricity that can be recognized and recorded using special equipment. An EMG test involves putting

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a small needle through the skin into a muscle and recording the pattern of electricity in the muscle when it is contracting.

Muscle biopsy muscle from patients with muscular dystrophy looks different from normal muscle when it is seen under a microscope. The small piece of muscle that is removed during the biopsy is cut into very thin slices, stained with a series of special dyes to show the different types of muscle fibers, and studied by a pathologist. A DNA blood test is used to analysis the X-chromosome (PCR-polymerase chain reaction). (Nowak, R.)

* Prognosis *

The prognosis of MD varies according to the type of MD and the progression of the disorder. Some cases may be mild and very slowly progressive, with normal lifespan, while other cases may have more marked progression of muscle weakness, functional disability and a loss of ambulation. Life expectancy may depend on the degree of progression and late respiratory deficit. In Duchenne muscular dystrophy, death usually occurs in the late teens to early twenties.

* Miscellaneous Information *

Something very important that parents with children with Duchenne muscular dystrophy should know is that these children can not use the normal anastasia. The normal anastasia will make their airway swell up and will not allow them to breathe.

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Let all your doctor?s and dentists know the child?s condition so they can mark this in their charts and records.

Testing individual muscles or muscle groups reveals a pattern of weakness, which is typical of DMD. Can DMD be diagnosed before these features are obvious? If parents have brought their son to a doctor at a very early stage of the disease, it may be difficult or impossible to detect anything definitely wrong on observing him. Doctors are therefore encouraged to test for DMD, with a blood test, whether they strongly suspect the diagnosis or regard it as just a possibility. The NINDS (National Institute of Neurological Disorders and Stroke) supports a broad program on research on MD. The goals of these studies are to increase understanding of MD and its cause(s), develop better therapies, and, ultimately, find ways to prevent and cure the disorder.

* Muscular Dystrophy Association *

What is MDA?

MDA was created in the 1950 by a group of adults with muscular dystrophy, parents of children with muscular dystrophy, and a physician-scientist studying the disorder. The Muscular Dystrophy Association is a voluntary national health agency?a dedicated partnership between scientists and concerned citizens aimed at conquering neuromuscular diseases that affect more than a million Americans. (Anderson, B.) Our local MDA office, one of one hundred and eighty-three nationwide, is available to

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serve anyone with one of the forty neuromuscular diseases in the association?s program.

Energized by its national chairman, Jerry Lewis, who has been the Association?s number-one volunteer for more than forty years, MDA today is one of the world?s leading voluntary health agencies fostering research and medical care.

Programs available through our local MDA office are funded almost entirely by individual private contributors. The Association receives no government grants, nor does it seek or receive fees from the people it serves or their families.

At this time there is no cure for DMD. The disability can be slowed by measures such as physical therapy, but cannot be stopped. Use of a wheelchair proceeds from occasional use at about age nine years to almost total dependence by the early teens. As the ability to walk is lost, the function of the hands and arms becomes increasingly important. Most function of the hands and arms becomes increasingly important. Most affected people survive in to their twenties, with a small minority surviving only to their late teens and a small number to more than thirty years of age.

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