Duchenne Muscular Dystrophy
The prevalence of DMD ranges between 1/3,500-1/ 9,300 male births. The prevalence of BMD varies from 1/16,700 to 1/18,500 male births. The prevalence of symptomatic female carriers is unknown.
Dystrophinopathies present with a spectrum of severity whereby BMD is at the mildest end and DMD the most severe, there is an intermediate phenotype in between. At the mildest end of the spectrum exercise-induced muscle cramps and myoglobinuria may be the only feature while at the severe end, there may be complete loss of muscle function, cardiomyopathy and respiratory failure. DMD presents in early childhood, motor milestones are delayed. Brain involvement leads to cognitive impairment (affecting about a third of patients) and/or pervasive behavioral disorders such as ADHD, autism, anxiety and OCD. Muscle hypertrophy is evident, especially in the calf muscles. Progression is rapid, such that by the age of 5 there is likely to be a waddling gait and positive Gowers’ sign. In untreated boys, walking is lost by 13 years of age (mean 9.5 years). Following loss of ambulation, scoliosis, respiratory failure and cardiomyopathy develop.
The pattern of inheritance is X-linked recessive. Genetic counselling of affected families is recommended and screening of women carriers in the family is important.
The clinical diagnosis can be confirmed by several methods. Creatine Kinase (CK) is very raised. Molecular genetic analysis by MLPA (multiplex ligation-dependent probe amplification) will show a deletion in 60%; full gene sequencing is necessary to identify small deletions, duplications and nonsense mutations. Muscle biopsy for dystrophin analysis which is absent in DMD and reduced in BMD.
Video of a Doctor describing the main points of the RD: Symptoms, Diagnosis, Experimental therapies etc
Management and treatment
There is no known cure for this group of dystrophinopathies. In DMD, treatment with corticosteroids stabilizes motor function and delays loss of ambulation and respiratory failure by several years. Physiotherapy and orthotics delay the onset of joint contractures. Non-invasive ventilation (NIV) to treat respiratory failure prolongs life expectancy. Regular cardiac monitoring from diagnosis with early treatment using ACE (angiotensin-converting enzyme) inhibitors and beta blockers stabilizes cardiomyopathy. For XLDCM, cardiac transplantation is the treatment of choice.
Life expectancy is shortened by cardiac and respiratory involvement, but can be substantially improved with regular monitoring and pro-active management.
The documents contained in this web site are presented for information purposes only. The material is in no way intended to replace professional medical care by a qualified specialist and should not be used as a basis for diagnosis or treatment
Expert reviewer(s): Dr Marina Katsalouli , Pr Maria Papadopoulos Last update: December 2020
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