What is DMD & BMD?
Duchenne Muscular Dystrophy (DMD) and Becker Muscular Dystrophy (BMD) Dystrophinopathies are diseases that are caused due to mutation in the dystrophin-coding gene, including Duchenne Muscular Dystrophy (DMD) and Becker Muscular Dystrophy (BMD). They are one of the most common neuromuscular diseases in Hong Kong. According to a local study, the prevalence of dystrophinopathies (including DMD and BMD) in Hong Kong is around 1.03 per 10 000 males. The global prevalence is 7.1 per 100,000 males. DMD is one of the most severe types of muscular dystrophies. It is an early onset disease which causes progressive muscle degeneration. Patients start to have symptoms since childhood.
Symptoms of DMD
- Falling frequently
- Difficulty climbing stairs, walking and running
- Difficulty performing daily activities
- Muscle pain
- In more severe cases, patients may have cardiac and respiratory problems as well, which may lead to death.
Quality of life of patients is affected and lifespan is shortened. Even though the life expectancy has increased with the help of treatment and management, most affected only survive until young adulthood.
BMD is a milder form of DMD, and is caused by the same gene but different mutations. Symptoms begin at a later age, and progressive muscle degeneration is slower. BMD patients generally have stronger muscles than DMD patients, and may survive till their 40s.
DMD and BMD are inherited diseases that can be passed on to the next generation through carriers of the defective gene. As they are X-linked recessive diseases, two copies of the defective gene (located on the X-chromosome) are required for the disease to develop. Therefore, mainly males are affected. Female cases of DMD patients are rare but they can be carriers of the defective gene and have a 50% chance of passing on the defective gene to their children.
Mutations and Testing
DMD is caused by mutations in the DMD gene, which encodes the dystrophin protein. The most common mutations include large deletions and large duplications. Other mutations include point mutations and insertions.
DMD can be tested by numerous methods, including blood tests, muscle biopsy, CGH-array, multiplex PCR, direct sequencing, and deletion/duplication analysis. Pangenia Genomics offers deletion/duplication analysis that accurately detects the number of copies of the DMD gene, i.e. find out if the gene or part of the gene is deleted or duplicated. It can be used for carrier screening as well.
Management and Treatment
- Nutrition management
- Surgery (for cardiac problems)
- Drugs to delay disease progression - Glucocorticoids (Prednisone / Deflazacort)
- FDA approved drug Eteplirsen for exon 51 skipping, so that the body is able to produce shorter but functional dystrophin hereby reducing the severity of the disease.
- Drug (Ataluren – licensed in Europe) to treat DMD cases with nonsense mutation.
 Crisafulli S, Sultana J, Fontana A, Salvo F, Messina S, Trifirò G. Global epidemiology of Duchenne muscular dystrophy: an updated systematic review and meta-analysis. Orphanet Journal of Rare Diseases. 2020;15(1).
 Chan S, Lo I, Cherk S, Cheng W, Fung E, Yeung W et al. Prevalence and Characteristics of Chinese Patients With Duchenne and Becker Muscular Dystrophy. Child Neurology Open. 2015;2(2):2329048X1558534.
 Landrum Peay H, Fischer R, Tzeng J, Hesterlee S, Morris C, Strong Martin A et al. Gene therapy as a potential therapeutic option for Duchenne muscular dystrophy: A qualitative preference study of patients and parents. PLOS ONE. 2019;14(5):e0213649.
 Queen Mary Hospital and The Duchess of Kent Children's Hospital at Sandy Bay, Hong Kong Paediatric Neuromuscular Diagnostic and Management Program [Internet]. Paed.hku.hk. 2020 [cited 12 November 2020]. Available from: