It typically presents itself when children are still learning to walk. Those affected will initially have difficulty standing up, walking and running. Eventually, boys will need a wheelchair to get around. MD may also affect the heart and respiratory muscles. Becker MD is similar to Duchenne, but the symptoms are less severe and usually do not develop until age 10 or later. These patients may have heart or breathing issues. Although Becker patients are likely to experience muscle and joint pain, most do not need a wheelchair.
Both types of MD affect predominantly affect boys because the mutated gene is situated on the X chromosome. Girls have two X chromosomes, while boys have one X and one Y chromosome, so even if a girl inherits the faulty gene the other healthy gene can compensate for the mutation.
Facioscapulohumeral and myotonic MD usually appear in the teen years and in adulthood, with myotonic MD being the most common late-developing type of MD.
Both conditions affect face and neck muscles. In addition to recognizing neuromuscular indicators of MD and reviewing family history, physicians may request several tests to definitively diagnose the disorder. Using a standard laboratory procedure, doctors can assess the blood levels of an enzyme, creatine kinase. Myotonia , or an inability to relax muscles following a sudden contraction, is found only in this form of MD, but is also found in other non-dystrophic muscle diseases.
People with DM1 can live a long life, with variable but slowly progressive disability. Typical disease onset is between ages 20 and 30, but childhood onset and congenital onset are well-documented. Muscles in the face and the front of the neck are usually first to show weakness and may produce a haggard, "hatchet" face and a thin, swan-like neck.
Wasting and weakness noticeably affect forearm muscles. DM1 affects the central nervous system and other body systems, including the heart, adrenal glands and thyroid, eyes, and gastrointestinal tract.
Other symptoms include cardiac complications, difficulty swallowing, droopy eyelids called ptosis , cataracts, poor vision, early frontal baldness, weight loss, impotence, testicular atrophy, mild mental impairment, and increased sweating. Individuals may also feel drowsy and have an excess need to sleep. There is a second form of the disease that is similar to the classic form, but usually affects proximal muscles more significantly.
This form is known as myotonic dystrophy type 2 DM2. This autosomal dominant disease affects both men and women. Females may have irregular menstrual periods and are sometimes infertile. The disease may occur earlier and be more severe in successive generations. A childhood-onset form of myotonic MD may become apparent between ages 5 and Symptoms include general muscle weakness particularly in the face and distal muscles , lack of muscle tone, and mental impairment.
A woman with DM1 can give birth to an infant with a rare congenital form of the disorder. Symptoms at birth may include difficulty swallowing or sucking, impaired breathing, absence of reflexes, skeletal deformities and contractures such as club feet , and muscle weakness, especially in the face. Children with congenital myotonic MD may also experience mental impairment and delayed motor development.
This severe infantile form of myotonic MD occurs almost exclusively in children who have inherited the defective gene from their mother, whose symptoms may be so mild that she is sometimes not aware that she has the disease until she has an affected child. The inherited gene defect that causes DM1 is an abnormally long repetition of a three-letter "word" in the genetic code.
In unaffected people, the word is repeated a number of times, but in people with DM1, it is repeated many more times. This triplet repeat gets longer with each successive generation. The triplet repeat mechanism has now been implicated in at least 15 other disorders, including Huntington's disease and the spinocerebellar ataxias. In the United States, the disease is most common in families of French-Canadian descent and among Hispanic residents of northern New Mexico.
People first report drooping eyelids, followed by weakness in the facial muscles and pharyngeal muscles in the throat, causing difficulty swallowing. The tongue may atrophy and changes to the voice may occur. Eyelids may droop so dramatically that some individuals compensate by tilting back their heads.
Affected individuals may have double vision and problems with upper gaze, and others may have retinitis pigmentosa progressive degeneration of the retina that affects night vision and peripheral vision and cardiac irregularities. Muscle weakness and wasting in the neck and shoulder region is common. Limb muscles may also be affected. Persons with OPMD may find it difficult to walk, climb stairs, kneel, or bend.
Those persons most severely affected will eventually lose the ability to walk. Both the individual's medical history and a complete family history should be thoroughly reviewed to determine if the muscle disease is secondary to a disease affecting other tissues or organs or is an inherited condition. It is also important to rule out any muscle weakness resulting from prior surgery, exposure to toxins, or current medications that may affect the person's functional status or rule out many acquired muscle diseases.
Blood and urine tests can detect defective genes and help identify specific neuromuscular disorders. For example:. Exercise tests can detect elevated rates of certain chemicals following exercise and are used to determine the nature of the MD or other muscle disorder.
Some exercise tests can be performed bedside while others are done at clinics or other sites using sophisticated equipment. These tests also assess muscle strength. They are performed when the person is relaxed and in the proper position to allow technicians to measure muscle function against gravity and detect even slight muscle weakness. If weakness in respiratory muscles is suspected, respiratory capacity may be measured by having the person take a deep breath and count slowly while exhaling.
Genetic testing looks for genes known to either cause or be associated with inherited muscle disease. DNA analysis and enzyme assays can confirm the diagnosis of certain neuromuscular diseases, including MD. Genetic linkage studies can identify whether a specific genetic marker on a chromosome and a disease are inherited together. They are particularly useful in studying families with members in different generations who are affected.
An exact molecular diagnosis is necessary for some of the treatment strategies that are currently being developed. Advances in genetic testing include whole exome and whole genome sequencing, which will enable people to have all of their genes screened at once for disease-causing mutations, rather than have just one gene or several genes tested at a time. Genetic counseling can help parents who have a family history of MD determine if they are carrying one of the mutated genes that cause the disorder.
Two tests can be used to help expectant parents find out if their child is affected. Diagnostic imaging can help determine the specific nature of a disease or condition. One such type of imaging, called magnetic resonance imaging MRI , is used to examine muscle quality, any atrophy or abnormalities in size, and fatty replacement of muscle tissue, as well as to monitor disease progression. MRI scanning equipment creates a strong magnetic field around the body. Radio waves are then passed through the body to trigger a resonance signal that can be detected at different angles within the body.
A computer processes this resonance into either a three-dimensional picture or a two-dimensional "slice" of the tissue being scanned.
MRI is a noninvasive, painless procedure. Other forms of diagnostic imaging for MD include phosphorus magnetic resonance spectroscopy, which measures cellular response to exercise and the amount of energy available to muscle fiber, and ultrasound imaging also known as sonography , which uses high-frequency sound waves to obtain images inside the body.
The sound wave echoes are recorded and displayed on a computer screen as a real-time visual image. Ultrasound may be used to measure muscle bulk. MRI scans of the brain may be useful in diagnosing certain forms of congenital muscular dystrophy where structural brain abnormalities are typically present.
Muscle biopsies are used for diagnostic purposes, and in research settings, to monitor the course of disease and treatment effectiveness. Using local or general anesthesia, a physician or surgeon can remove a small sample of muscle for analysis. The sample may be gathered either surgically, through a slit made in the skin, or by needle biopsy , in which a thin hollow needle is inserted through the skin and into the muscle. A small piece of muscle remains in the hollow needle when it is removed from the body.
The muscle specimen is stained and examined to determine whether the person has muscle disease, nerve disease neuropathy , inflammation, or another myopathy. Muscle biopsies can sometimes also assist in carrier testing. With the advent of accurate molecular techniques, muscle biopsy is less frequently needed to diagnose muscular dystrophies.
Muscle biopsy is still necessary to make the diagnosis in most of the acquired muscle diseases. Immunofluorescence testing can detect specific proteins such as dystrophin within muscle fibers.
Following biopsy, fluorescent markers are used to stain the sample that has the protein of interest. Electron microscopy can identify changes in subcellular components of muscle fibers.
Electron microscopy can also identify changes that characterize cell death, mutations in muscle cell mitochondria, and an increase in connective tissue seen in muscle diseases such as MD. Changes in muscle fibers that are evident in a rare form of distal MD can be seen using an electron microscope. All forms of MD are genetic and cannot be prevented at this time, aside from the use of prenatal screening interventions.
However, available treatments are aimed at keeping the person independent for as long as possible and prevent complications that result from weakness, reduced mobility, and cardiac and respiratory difficulties.
Treatment may involve a combination of approaches, including physical therapy, drug therapy, and surgery. The available treatments are sometimes quite effective and can have a significant impact on life expectancy and quality of life. Assisted ventilation is often needed to treat respiratory muscle weakness that accompanies many forms of MD, especially in the later stages.
Air that includes supplemental oxygen is fed through a flexible mask or, in some cases, a tube inserted through the esophagus and into the lungs to help the lungs inflate fully. Since respiratory difficulty may be most extreme at night, some individuals may need overnight ventilation.
Many people prefer non-invasive ventilation, in which a mask worn over the face is connected by a tube to a machine that generates intermittent bursts of forced air that may include supplemental oxygen. Some people with Duchenne MD, especially those who are overweight, may develop obstructive sleep apnea and require nighttime ventilation. Individuals on a ventilator may also require the use of a gastric feeding tube. Drug therapy may be prescribed to delay muscle degeneration. The U. Food and Drug Administration FDA has approved injections of the drugs golodirsen and viltolarsen to treat Duchenne muscular dystrophy DMD patients who have a confirmed mutation of the dystrophin gene that is amenable to exon 53 skipping.
It is estimated that about 8 percent of patients with DMD have this mutation. The FDA has approved injection of the drug casimersen to treat patients who have a confirmed mutation of the DMD gene that is amenable to exon 45 skipping. Corticosteroids such as prednisone can slow the rate of muscle deterioration in Duchenne MD and help children retain strength and prolong independent walking by as much as several years.
However, these medicines have side effects such as weight gain, facial changes, loss of linear height growth, and bone fragility that can be especially troubling in children. Immunosuppressive drugs such as cyclosporine and azathioprine can delay some damage to dying muscle cells. Drugs that may provide short-term relief from myotonia muscle spasms and weakness include mexiletine; phenytoin; baclofen, which blocks signals sent from the spinal cord to contract the muscles; dantrolene, which interferes with the process of muscle contraction; and quinine.
The Food and Drug Administration has granted accelerated approval of the drug Exondys 51 to treat individuals who have a confirmed mutation of the dystrophin gene amenable to exon 15 skipping. The accelerated approval means the drug can be administed to selected individuasl who meet the rare disease criteria while the company works on additional trials to learn more about the effectiveness of the drug.
Drugs for myotonia may not be effective in myotonic MD but work well for myotonia congenita, a genetic neuromuscular disorder characterized by the slow relaxation of the muscles. Respiratory infections may be treated with antibiotics. Physical therapy can help prevent deformities, improve movement, and keep muscles as flexible and strong as possible.
Options include passive stretching, postural correction, and exercise. A program is developed to meet the individual's needs. Therapy should begin as soon as possible following diagnosis, before there is joint or muscle tightness. Occupational therapy may help some people deal with progressive weakness and loss of mobility.
Some individuals may need to learn new job skills or new ways to perform tasks while other persons may need to change jobs. Assistive technology may include modifications to home and workplace settings and the use of motorized wheelchairs, wheelchair accessories, and adaptive utensils.
Speech therapy may help individuals whose facial and throat muscles have weakened. Individuals can learn to use special communication devices, such as a computer with voice synthesizer. Dietary changes have not been shown to slow the progression of MD. Proper nutrition is essential, however, for overall health. Limited mobility or inactivity resulting from muscle weakness can contribute to obesity, dehydration, and constipation.
A high-fiber, high-protein, low-calorie diet combined with recommended fluid intake may help. Feeding techniques can help people with MD who have a swallowing disorder and find it difficult to pass from or liquid from the mouth to the stomach.
The prognosis varies according to the type of MD and the speed of progression. Some types are mild and progress very slowly, allowing normal life expectancy, while others are more severe and result in functional disability and loss of ambulation. The goals of these studies are to increase understanding of MD and its causes, develop better therapies, and, ultimately, find ways to treat it. Advances in basic research are essential to the basic understanding of each type of MD. While many genes that cause muscular dystrophy still remain to be identified, advances in gene sequencing has aided the identification of genes that may be involved for most types of muscular dystrophy.
In turn, new knowledge of specific disease mechanisms is identifying potential targets for therapy development. In recent years, research into the underlying disease mechanisms has created new opportunities for therapy development in nearly all types of MD.
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. On Sept. On Feb. Skip to main content. Search MDA. Search Donate. What causes DMD? What is the life expectancy in DMD? What is the status of DMD research? Parsippany, NJ.
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