3)
A 5-year-old boy presents with weakness in his legs. He has trouble with exercise programs at school, significantly more frequently than his classmates. He is uncoordinated, grew considerably slower than his brothers, and often had difficulties in hopping and trying to climb. A physical examination demonstrates proximal muscle fatigue. Laboratory testing shows an elevated creatine kinase. A genetic test reveals an abnormality on his X chromosome. Which of the following will slow the progression of muscle weakness?
