Duchenne muscular dystrophy and becker muscular dystrophy

[Marquetta]

Muscular dystrophies are a group of inherited muscle disorders in which one or more genes needed for normal muscle structure and function are defective, leading to muscle weakness of varying severity. Duchenne muscular dystrophy and Becker muscular dystrophy cause weakness in the muscles closest to the torso.

These dystrophies are caused by defects in genes responsible for muscle function, which lead to muscle weakness that develops during childhood or adolescence, and nearly always occur in boys.
Both dystrophies are characterized by physical weakness.
The diagnosis is based on the results of tests done on samples of blood and a sample of muscle tissue.
Treatment includes physical therapy and sometimes surgery for both dystrophies and prednisone or deflazacort for Duchenne dystrophy.

Duchenne muscular dystrophy is the second most common (facioscapulohumeral dystrophy is the most common) and the most severe form of muscular dystrophy. It begins during early childhood. Becker muscular dystrophy, although closely related to Duchenne muscular dystrophy, begins later during adolescence and causes milder symptoms. These dystrophies nearly always occur in boys. Together, Duchenne muscular dystrophy and Becker muscular dystrophy affect 5 of 1,000 people. Most people have Duchenne muscular dystrophy.
The gene defect that causes Duchenne muscular dystrophy is different from the gene defect that causes Becker muscular dystrophy, but both defects involve the same gene, called the dystrophin gene. The gene for either of these traits is recessive and is carried on the X chromosome. Therefore, although a female can carry the defective gene, she will not develop the disease because the normal gene on one X chromosome compensates for the gene defect on the other X chromosome. However, any male who receives the defective gene will have the disease because males have only one X chromosome (see Inheritance Patterns : X-Linked Inheritance).
Boys with Duchenne muscular dystrophy lack almost all of the muscle protein dystrophin, which is important for maintaining the structure of muscle cells. Boys with Becker muscular dystrophy produce dystrophin, but because the protein structure is altered, the dystrophin does not function properly or the amount of dystrophin is insufficient.

[Michiko]

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.