Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a gentic disorder in which an individual's muscles deteriorate at an abnormally fast pace. It is one of nine types of muscular dystrophy, a group of genetic, degenerative diseases primarily affecting voluntary muscles. DMD is caused by a defective gene for dystrophy, a protein that keeps muscle cells intact; however, there have been cases where there was no known history of DMD in the family lineage. DMD occurs in approximately 1 out of every 3,600 male infants.

Symptoms


Symptoms appear in the individual as early as infancy and up to six years old and consist of: Fatigue, mental retardation, andmuscle weakness. DMD effects voluntary muscle, or skeletal muscle. Weakness starts in the legs but gradually moves up to the arms, neck, and other parts of the body. The deterioration of the muscles causes many problems within the body. It is the mostimportant symptom that the disease causes. Basic motor skills are severly affected by the disease. The Infected person cannot walk, run, or do many physical activities. Unlike other muscular dystrophy disorders, DMD rapidly worsens; at the age ten a child may need the use of a brace and at the age twelve a child may lose all walking abilities.

Diagnosis
To diagnose DMD, many doctors will perform a complete neurological, heart, lung and muscle exam. Some of the results will show abnormal heart muscle (cardiomyopathy), deformities of the chest and back, called scoliosis, enlarged calf muscles, which eventually get replaced by fat and connective tissue (pseudohypertrophy), muscle atrophy, muscle cramps, muscle deformaties, and respiratory disorders. Other rare results of the test are congestive heart failure or irregular heart rhythym, called arrhythmias. Another set of tests are done when these results appear in the patient, these tests include: Genetic Tests, Electromyography (EMG), Muscle Biopsy, and Creatine Phosphokinase (CPK).

Electromyography tests (EMG) the health of muscles and the nerves that controls the muscles. When this test is performed, a very needle electrode is inserted into the muscle. The electrode picks up the electrical activity given off by the muscles. A special monitor, called an oscilloscope, is used to display the activity within the muscle. The doctor, or practitioner, performing the test will ask to contract the muscle. Waves will form on the screen of the oscilloscope and it displays the action potential, or the muscle's ability to respond when the muscles are stimulated. Sounds will also come from the machine and when the needle is initially inserted the sounds will be loud, but they will quiet down. Then, when the muscle is contracted again the sounds will be loud continually because of the activity of the action potentials. However, in a patient with DMD the sounds can remain quiet because the neurological signals will not be transmitted.

Another test to show muscle health is a muscle biopsy. The doctor will take a piece of the muscle for examination. The test is usually done while the patient is awake and a local anesthesia is applied to the biapsy area. Two types of biapsies are available to patients. One type, the needle biopsy, involves the insertion of a needle in the muscle. When the needle is removed from the muscle, it takes a piece of the it with it and the muscle tissue is used in the labratory for examination. The other type, the open biopsy, involves the incision of the skin and muscle, where muscle tissue is removed. Normal results of this test will show that the muscle tissure is healthy and and has normal tissure anatomy; however, a patient with DMD will show abnormal tissue structure and when the muscle is stained and examined by a microscope it will show that the tissue is atypical.

The Creatine Phosphokinase (CPK) test is a blood test that shows the levels of the enzyme, CPK. Practitioners draw blood from the vein and put it in an air tight vile, which is then sent to a lab, where the CPK amount it taken. In a normal patient the CPK level will be relatively low; in a patient with DMD the CPK levels will be very high, meaning that there is a stress on the heart, brian, or muscle.

Treatment
There is no known treatment of this disorder. Most treatments that are done help the patients quality of life to be better, but do not cure the person completely. Most doctors recommend that the patient stay active, since best-rest can lead to more complications. Physical therapy can also help maintain muscle strength and function and the use of wheelchairs and braces may increase mobility. In the later future, Gene Therapy may be available.

Life Expectancy/Quality of Life
DMD leads a life of a quickly developing disability, meaning that a patient with DMD will not live a very long life. The life expectancy is up to twenty-five years of age. However, there have been cases where a person with DMD has lived up to thirty years. A person with DMD must use a wheelchair or a brace, fore most of their lives, when moving from place to place. Death usually occurs from the organs in the body getting infected, usually the lungs.

Inheritance
DMD is a X-linked gene, which means that it primarily effects boys. Women are usually carriers of this gene and when they give birth to a new born boy it gets passed on. The sons of a female with DMD have a 50% chance of inheriting the gene and the daughters have a 50% chance of becoming carriers.

Sources

http://www.nlm.nih.gov/medlineplus/ency/article/000705.htm

https://health.google.com/health/ref/Duchenne+muscular+dystrophy