Review Question - QID 109906

A 6-year-old boy presents to his pediatrician’s office for muscle weakness. The patient is accompanied by his mother who states that he has difficulty running and walking up stairs. The mother has noticed mild weakness when the patient attempts to sit up from a supine position since he was 4-years-old. Medical history is significant for fractures involving the arms and legs secondary to falling. His temperature is 98.6°F (37°C), blood pressure is 105/63 mmHg, pulse is 92/min, respirations are 18/min, and oxygen saturation is 99% on room air. On physical exam, the child does not appear to be in distress and is conversational. He has a waddling gait along with lumbar lordosis and bilateral calf enlargement. The patient uses his hands to push himself into an upright position when rising from the floor. He has absent patellar and ankle-jerk reflexes. Which of the following is the most appropriate next step in management?