Fact sheet 3 Duchenne Muscular Dystrophy & Becker Muscular Dystrophy What are Muscular Dystrophies? Most affected adolescents develop a sideways The muscular dystrophies are a group of genetic curvature of the spine called sco liosis, which disorders that are characterised by progressive may impair breathing and adds to discomfort. muscle weakness. There are differences in the Few surv ive beyond the third decade, with various types of muscular dystrophy in the rate respiratory complications and heart disease at which the muscle weakness progresses and being common causes of death. Division of Human the muscle groups wh ich are most severely Genetics affected. The age of onset at wh ich symptoms University of Cape Intellectual ability is usually normal in people first appear in the different types varies from Town with DMD, although intellectual disability is childhood through adult life. found to occur in these indiv iduals more often This fact sheet focuses on two particular types of muscular dystrophy: Duchenne muscular than in the general population. Unlike the dystrophy (DMD) and Becker muscular physical disability, the mental handicap, if present, is not progressive. dystrophy (BMD). Both DMD and BMD affect males A very small number (5-10%) of female carriers predominantly, affected females are very rare. of the “faulty” gene have a mild degree of muscle weakness themselves and are then Figure 1 shows the muscles that are affected during the early stage of Duchenne and Becker known as „manifesting carriers‟. However, it is extremely rare for a female to show symptoms. muscular dystrophy . What are the features of Becker muscular dystrophy (BMD)? Figure 1: In the early BMD is characterised by the same pattern of stages, Duchenne and muscle weakness but is less severe and Becker muscular disabling than DMD. BM D usually has a later dystrophy affect the onset than DMD and is sometimes only pectoral muscles - which diagnosed during adolescence or adulthood. draw back the shoulders, The effects of BMD on the joints, spine, heart the trunk and the upper and lower legs. These and lungs are generally milder. BMD is, weaknesses lead to however, very variable in severity, even difficulty in rising, between affected family members. Some climbing stairs and people with BMD are able to walk only until maintaining balance. early adulthood, others to an advanced age. (Picture from the Muscular Survival in some affected people is to middle Dystrophy Association website: age, but others have survived more than 80 http://www.mdausa.org/) years. Some develop heart problems in early adulthood; others never do. What are the features of Duchenne muscular GENETICS: dystrophy (DMD)? As this is a genetic condition, genetic Duchenne muscular dystrophy usually presents counselling is strongly recommended. Genetic in early childhood with delayed milestones, counselling provides information on the including delays in standing independently. The condition, its inheritance pattern, risks to other first thing parents usually notice is that the calf family members and the prognosis (probable muscles are enlarged. By approximately 8 to 11 outcome). Psycho-social support and years of age affected boys are unable to walk information about testing, includin g diagnostic and most are wheelchair bound by age 12 years testing, carrier testin g, presymptomatic and of age. Heart disease occurs in all patients after prenatal testing (when appropriate and age 18. Shortening of some muscles leads to a available) is offered. typical pattern of restriction of joint movement called contractures. The resources in this brochure should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic condition should consult a qualified healthcare professional. Fact sheet 3 Duchenne Muscular Dystrophy & Becker Muscular Dystrophy How common is DMD and BMD? When is Genetic Testing appropriate? DMD is one of the most frequent forms of Genetic testing can be done to confirm a muscular dystrophy, affecting approximately diagnosis (a diagnostic test), determine 22 per 100 000 male births, while BMD affects whether a person is a carrier for DM D or 3 per 100 000 male births. Of DMD patients, BMD (carrier testing) or to p redict if a person Division of Human 60% have inherited the “faulty” gene or an unborn child will develop DM D or Genetics (mutation) from one of their parents (familial BMD (a predictive or a prenatal test). University of Cape mutations). In 30% of DM D patients the Town genetic change occurs for the first time in the Genetic serv ices should be rendered with formation of the egg or the sperm; this is called comprehensive genetic counsellin g. The a spontaneous mutation. In these cases the Div ision of Human Genetics at the University affected person would be the first in the family of Cape Town can be contacted in this regard. to have the mutation. Spontaneous mutations occur less frequently in BMD patients (approximately 10%). How soon will I have the results? Results will be available within approximately What genes are related to DMD and BMD? 4 weeks of the test. The results will be communicated to you personally via your DMD is caused by mutations in the dystrophin general practitioner, neurologist o r by the gene. The dystrophin gene is located on the X staff of the Div ision of Human Genetics at the chromosome and when a fault (mutation) University of Cape Town. occurs it leads to the formation of a faulty protein in muscle f ibres. The dystrophin protein is absent or non-functional in DMD. Is there treatment available for DMD and Whereas in BMD the type of fault (mutation) BMD? makes the dystrophin molecule abnormal. It is Currently there is no known treatment that still able to function, but to a lesser degree than alters the actual loss of muscle cells. Much normal. Having some dystrophin protects the can be done to help limit the effects of the muscles of those with BMD from degenerating muscular dystrophy. Steroids may help to as badly or as quickly as those of people with delay disease progression, but should only be DMD. The function of dystrophin in the used under strict medical supervision. muscle fibre is complex, but we know that Prevention of scoliosis is one of the main when it is absent or abnormal the muscles challenges in the treatment of affected slowly become weaker. individuals. Back support and surgery is used to combat this. The discovery of the How do people inherit DMD or BMD? dystrophin gene and knowledge of the function of the protein has raised hope that The dystrophin gene is carried on the X rational therapeutic strategies will be chromosome and inherited in an X-linked developed. recessive manner. (Refer to Fact sheet 11.) The resources in this brochure should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic condition should consult a qualified healthcare professional. Fact sheet 3 Duchenne Muscular Dystrophy & Becker Muscular Dystrophy Where can I read more about DMD and BMD? You may find the following recourses about Muscular Dystrophies helpful. 1. Genetics Reviews: http://www.genetest.org/ Division of Human Genetics University of Cape 2. Muscular Dystrophy Association website: Town http://www.mdausa .org/ 3. Muscular Dystrophy Foundation (MDF) of South Africa: http://www.mdsa.org.za/ Are there DMD and BMD support groups? The DMD and BMD support groups in South Africa falls under the Muscular Dystrophy Foundation of South Africa. Please contact your local MDF office for information. • National Office: P.O. Box 1535, Pinegowrie, 2123 Tel: (011) 789-7634, Fax: (011) 789-7634 Email: firstname.lastname@example.org • Cape Branch: P.O. Box 752, Goodwood, 7459 Tel: (021)592-7306, Fax: (021)592-7306 Email: email@example.com Who do I contact for more information regarding testing? Division of Human Genetics Molecular Laboratory: Prof. Jacquie Greenberg (021) 406-6299 Dr Rene Goliath (021) 406-6433 Genetic Nurses: Sister Sklar and Sister Legg (021) 406-6304 The resources in this brochure should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic condition should consult a qualified healthcare professional.
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