This muscle weakness causes a waddling gait and difficulty climbing stairs. Muscle weakness also occurs in the arms, neck, and other areas, but not as severely or as early as in the lower half of the body.
Calf muscles initially enlarge and the enlarged muscle tissue is eventually replaced with fat and connective tissue pseudohypertrophy. Muscle contractures occur in the legs, making the muscles unusable because the muscle fibers shorten and fibrosis occurs in connective tissue.
Occasionally, there can be pain in the calves. Symptoms usually appear in boys aged 1 to 6. There is a steady decline in muscle strength between the ages of 6 and 11 years. By age 10, braces may be required for walking, and by age 12, most boys are confined to a wheelchair. Bones develop abnormally, causing skeletal deformities of the spine and other areas.
Muscular weakness and skeletal deformities frequently contribute to breathing disorders. Cardiomyopathy enlarged heart occurs in almost all cases, beginning in the early teens in some, and in all after the age of 18 years. Intellectual impairment may occur, but it is not inevitable and does not worsen as the disorder progresses.
Few individuals with DMD live beyond their 30s. Breathing complications and cardiomyopathy are common causes of death.
Duchenne muscular dystrophy is diagnosed in several ways. A clinical diagnosis may be made when a boy has progressive symmetrical muscle weakness. The symptoms present before age 5 years, and they often have extremely elevated creatine kinase blood levels which are described below. If untreated, the affected boys become wheelchair dependent before age 13 years.
A muscle biopsy taking a sample of muscle for dystrophin studies can be done to look for abnormal levels of dystrophin in the muscle. The dystrophin protein can be visualized by staining the muscle sample with a special dye that allows you to see the dystrophin protein. A muscle which has average amounts of dystrophin will appear with the staining technique as though there is caulking around the individual muscles cells and it is holding them together like window panes.
A boy with Duchenne, on the other hand, will have an absence of dystrophin and appear to have an absence of the caulking around the muscle cells. Some individuals can be found to have an intermediate amount of the dystrophin protein.
Often these boys are classified as having Becker muscular dystrophy. Genetic testing looking at the body's genetic instructions on a blood sample for changes in the DMD gene can help establish the diagnosis of Duchenne muscular dystrophy without performing a muscle biopsy. Those individuals who are not found to have a detected change in the DMD gene using this method, and who are diagnosed with DMD by biopsy, still have a change in their gene but it is in areas of the gene that are not examined using these methods.
However, the results of genetic testing may not be conclusive of a diagnosis of DMD, and only the muscle biopsy can tell the level of dystrophin protein for sure. Duchenne muscular dystrophy also called Duchenne MD or DMD is the most common form of muscular dystrophy , a genetic disorder that gradually makes the body's muscles weaker.
Duchenne MD is progressive, meaning problems get worse with age. As kids with DMD become teens, muscle weakness throughout the body can lead to heart and breathing problems. Duchenne MD happens because of a lack of dystrophin dis-TRO-fin , a protein made by the muscle cells. In DMD, a variation or missing part of the dystrophin gene causes a loss of the dystrophin protein.
This protein loss prevents the muscle fibers from working properly, leading to weakness. Duchenne MD affects boys more often than girls because the dystrophin gene is on the X chromosome.
Boys have only one X chromosome and girls have two. So girls can almost always make working dystrophin using the dystrophin gene on their second X chromosome. But girls with a Duchenne MD gene may still have muscle cramps, weakness, and heart problems. Women with a deletion or variation in the gene are carriers and can pass this on to their children. Sometimes the variation or deletion in the gene does not come from the mother, but is a new change in the child.
This is called a de novo or new variation. Doctors often diagnose muscular dystrophy based on the child's family history, symptoms, and an exam. A child with Duchenne MD usually is cared for by a team of doctors and other experts from several pediatric specialties.
Treatment advances let kids with Duchenne MD live longer, more active lives than would have been possible 10 or 20 years ago. Reviewed by: Mena T. Thanks to advances in cardiac and respiratory care, life expectancy is increasing and many young adults with DMD attend college, have careers, get married, and have children. Survival into the early 30s is becoming more common than before.
MDA-supported researchers are actively pursuing several exciting strategies in DMD, such as gene therapy , exon skipping , stop codon read-through and gene repair. Human clinical trials are underway for some of these strategies. For an overview of DMD research strategies and the latest research news, see Research.
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