An 11-year-old girl child, father c/o abnormal gait one year and frequent fall while running two years. O/E: Gastrocnemius muscles are looking hypertrophied while rest of leg muscles are showing marked wasting, power zero, unable stand and sit independently. Upper limbs are also wasted and weak. Her physical growth is also arrested.

CBC normal, only S. CPK is 4950, muscle biopsy not done. Which is this disease?