Duchenne muscular dystrophy and Becker muscular dystrophy are X-linked recessive disorders characterized by progressive proximal muscle weakness caused by muscle fiber degeneration. Becker dystrophy has later onset and causes milder symptoms. Diagnosis is suggested clinically and is confirmed by genetic testing or analysis of the protein product (dystrophin) of the mutated gene. Treatment focuses on maintaining function through physical therapy and the use of braces and orthotics. Patients who have Duchenne dystrophy should be offered prednisone or deflazacort and sometimes exon-skipping treatments using antisense oligonucleotides.
Muscular dystrophies are inherited, progressive muscle disorders resulting from defects in one or more genes needed for normal muscle structure and function; dystrophic changes (eg, muscle fiber necrosis and regeneration) are seen on biopsy specimens.
Duchenne dystrophy and Becker dystrophy are the second most prevalent muscular dystrophy (after facioscapulohumeral muscular dystrophy). They are caused by mutations of the dystrophin gene, the largest known human gene, at the Xp21.2 locus. About 70% of Duchenne dystrophy is caused by a single- or multiexon deletion or duplication. In Becker dystrophy, 85% of patients have a deletion, and 10% have a duplication.
In Duchenne dystrophy, these mutations result in the severe absence (lt; 5%) of dystrophin, a protein in the muscle cell membrane. In Becker dystrophy, the mutations result in production of abnormal dystrophin or insufficient dystrophin.
Duchenne dystrophy and Becker dystrophy together affect 5/1000 people; the majority have Duchenne. Female carriers may have asymptomatic elevated creatine kinase levels and possibly calf hypertrophy.
Muscular
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