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SPRING 2025 InTouch | 17 One third of DMD and BMD cases are spontaneous, so it is possible to be a Manifesting Carrier without a family history. MANIFESTING CARRIERS OF DUCHENNE OR BECKER MUSCULAR DYSTROPHY or other genetic mechanisms, the healthy X chromosome is less active, and symptoms appear. On rare occasions, a female may lack a second X chromosome entirely, or it may have been damaged during development and is therefore unable to mask the effects of DMD or BMD. Alternatively, through a mechanism called “skewed X-inactivation,” the body’s cells rely more on the X chromosome carrying the defect and less on the healthy X chromosome, resulting in the development of symptoms. The dystrophin gene is very large, making it prone to mutation, and nearly one-third of cases occur “de novo,” or spontaneously, without a family history. For further information on genetics and inheritance, please refer to the Genetics Factsheet. The Muscular Dystrophy Association’s Becker Muscular Dystrophy and Duchenne Muscular Dystrophy Factsheets provide a more in-depth look into these disorders. Diagnosis Diagnosis usually begins after the identification of early symptoms in manifesting carriers of DMD or BMD, such as muscle pain, weakness, or cardiac problems, and generally includes: • Genetic testing: A blood test to identify pathogenic changes in the dystrophin (DMD) gene, which confirms the diagnosis in most cases. • Blood tests: Measurement of creatine kinase (CK) levels, which are usually elevated in affected individuals, reflecting ongoing muscle breakdown. • Cardiac assessment: Electrocardiogram (ECG), echocardiogram, and/or cardiac MRI to assess heart function. • Electromyography (EMG): A test that measures the electrical activity in muscles, helping to determine if muscle weakness is due to a primary muscle disorder. • Muscle biopsy: Rarely required due to advances in genetic testing, but may show reduced or patchy dystrophin expression if performed. Individuals are sometimes misdiagnosed due to the similarity of symptoms between manifesting carriers and limb-girdle muscular dystrophy. It is important to differentiate between the two. Following a diagnosis in the family, genetic counselling should be arranged. Genetic services in New Zealand are available, and a referral can be made by the Muscular Dystrophy Association (MDA). Management There is no cure for DMD or BMD, but symptoms can be managed and monitored. • Exercise: From an early stage, regular exercise and stretching programmes, ideally with the guidance of a physiotherapist, Continued over ... Above: Mitochondrial DNA is only inherited from the Mother. Mitochondrial Father unaffected Father affected Mother affected Mother unaffected Children affected Children unaffected