This is Duchenne muscular dystrophy. There is degeneration of muscle fibers along with some regeneration and scattered chronic inflammatory cells, fibrosis, and hypertrophy of remaining muscle fibers. Duchenne's is due to a defective gene on the X chromosome that leads to an inability to produce the membrane skeletal protein dystrophin. Thus, this is an X-linked recessive disorder. About 30% of cases represent new mutations.

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