The relatively thick calf muscles suggest Duchenne muscular dystrophy. M. Becker usually presents in adulthood, so if this is a kid I think its DMD.
Duchenne's muscular dystrophy: the increased circumference of the calves are a result of accumulations of fat and connective tissue in the presence of relatively normal amounts of muscle tissue.
Correct answer - This is Pseudohypertophy of the calves because of replacement of muscle fibers by fat and fibrous tissue... can occur in muscular dystrophy like Duchenne's and Becker's as this is a pediatric case more likely this is Duchenne's muscular dystorpy...