X-chromosome linked diseases Duchenne and Becker Muscular Dystrophies Duchenne and Becker muscular dystrophies cause weakness in the muscles closest to the torso These dystrophies are the most common muscular dystrophies and nearly always occur in boys On average, 1 of 3, 300 boys born has duchenne dystrophy, whereas on average 1 of 18,000 boys born has Becker muscular dystrophy Boys with Duchenne muscular dystrophy lack almost totally 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.Duchenne and Becker Muscular Dystrophies Duchenne and Becker muscular dystrophies cause weakness in the muscles closest to the torso . These dystrophies are the most common muscular dystrophies and nearly always occur in boys. On average, 1 of 3,300 boys born has Duchenne dystrophy, whereas on average 1 of 18,000 boys born has Becker muscular dystrophy. Boys with Duchenne muscular dystrophy lack almost totally 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. X-chromosome linked diseases