pediatrics
Duchenne Muscular Dystrophy and Becker Muscular Dystrophy
Introduction
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 is focused on maintaining function through physical therapy and the use of braces and orthotics. Patients who have Duchenne dystrophy should be offered 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. gene, the largest known human gene, at the Xp21.2 locus. Up to 70% of Duchenne dystrophy is caused by a single- or multiexon deletion, approximately 10% by a duplication and 20% by a point mutation. In Becker dystrophy, approximately 70% of patients have a deletion, 20% have a duplication, and up to 10% are point mutations ( General reference ). In Duchenne dystrophy, these mutations result in the severe absence (<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 about 1/5000 to 1/6000 live male births ( General reference ); the majority have Duchenne. Female carriers may have asymptomatic elevated creatine kinase levels and possibly calf hypertrophy. 