Q. A 12-year-old boy is brought to the physician’s office by his mother for follow-up with a history of slowly progressive muscle weakness. She first noticed muscle weakness at 4 years of his age. Initially, he had difficulty in activities such as running, jumping, and climbing stairs. Subsequently, symptoms such as difficulty in walking and frequent falling have appeared. Presently, he is wheelchair-bound. His temperature is 98.6°F (37°C), pulse is 92 beats per minute, BP is 110/70 mm of Hg and respiratory rate is 15/min. On physical examination, he shows a weakness in the muscles of both upper and lower limbs. When rising from the floor, he uses his hand to push himself up. He also has significant wasting in the muscles of upper and lower limbs, except in the calf area where significant hypertrophy is noted. Skeletal examination shows lumbar lordosis and scoliosis. Cardiac and lung examinations are normal. He has a waddling gait. The creatine kinase level is 164 U/L. What is the mode of inheritance of the disease in this patient?