About Muscular Dystrophy
Muscular dystrophies are defined as a group of genetic disorders characterized by progressive muscle wasting and weakness. Duchenne Muscular Dystrophy (DMD) is the most common form of muscular dystrophy. In fact, in the list of muscular dystrophy sufferers available to the Association, most of them suffer from Duchenne. Hence, focus is given to Duchenne muscular dystrophy on our website.
DMD is a fatal disease that is characterized by rapid and progressive muscle weakness and atrophy of muscle tissue starting in the legs and pelvis and later affecting the whole body. DMD affects mostly young males, due to its X-linked recessive inheritance pattern. Two-thirds of DMD incidences are caused by genetic inheritance from the mother, while the remainder is caused by mutations in the genes of the egg or embryo. It affects about 1 out of every 3 500 boys. Girls can carry the gene that causes the disease, but they usually show no symptoms.
In 1986, muscular dystrophy researchers identified the gene that, when flawed - a problem known as a mutation - causes DMD. The protein associated with that gene was identified and named dystrophin. It helps keep muscle cells intact, but is absent in DMD patients.
The disease manifests itself in early childhood at the age of about 2 to 6 years. The symptoms are generalised weakness and muscle wasting, first affecting the muscles of the hips, pelvic area, thighs and shoulders. Calves are often enlarged. The progression of the disease naturally varies from one patient to the other, and it is difficult to predict exactly when an individual will lose a particular function or how long one person will survive. However, observations of large number of cases have revealed certain average tendencies described below.
Parents may note that the boy is clumsy and falls often. As time goes by, however, the falls clearly begin to look more ominous. By the age of 3 or 4 years, the boy cannot keep up with his peers, has trouble with climbing stairs or playground equipment or getting up from the floor, and usually cannot manage to run. Jumping from a standing position with both feet is almost always impossible.
By school age, the problem is obvious. The child has trouble walking, mostly because the quadriceps muscles, the large 'lap' muscles in the front of the thighs, are weakening, keeping him off balance as he tries to shift his weight. To compensate, the boy contracts the muscles in the back of the lower leg (calf muscles), which in turn causes the foot to go down and the toes to point. He may walk on his toes or the balls of his feet, with a slightly rolling gait.
By the age of ten, on average, the boy has difficulty in getting up from a chair or floor, climbing up the stairs, or walking unassisted. By the age of twelve, the boy is confined to a wheelchair fulltime. His health and life is threatened by the damage caused to the heart muscles, leading to loss of respiratory muscle power and cardiac complications.
Some boys with DMD seem to have no difficulties at all with learning or memory formation, while others have significant impairment in those areas. Whether or not brain dystrophin is affected and to what extent is probably related to the specific genetic mutation and other aspects of DNA processing. However, studies have shown that, as a group, children affected by the disease have a mean IQ of around 90, compared with 100 for the general population. Unlike the physical aspects of DMD which worsen progressively, the cognitive skills are not progressively affected. If anything, the cognitive issues improve over time as the child grows, suggesting 'delay' rather than 'deficit' on some areas.
Duchenne Muscular Dystrophy eventually affects all voluntary muscles, including the heart and breathing muscles. Death typically occurs from respiratory failure or heart disorders. Survival is rare beyond the early 30s, although recent advancements in medicine are extending the lives of those afflicted. Studies in Denmark have revealed that some patients live to their early 40s, as a result of proper and intensive management of the disease. The ordinary adult patient describes his quality of life as: "excellent, and worries neither about the disease nor about the future." Despite heavy immobilization, he is still capable of functioning in a variety of activities that are associated with normal life. Unfortunately, the prospect of a typical Mauritian patient is shockingly bleak, as his conditions are not properly monitored and managed.