At least half of affected boys do not walk until eighteen months of age or later. In retrospect, almost all parents have noted that their child never walked or ran normally. Over the first few years of life these children have difficulty climbing and getting up from the floor. Parents often comment that their child falls frequently. The boys are not able to keep up with their friends in physical activities at kindergarten or school and they are often regarded as clumsy or lazy.
Some parents notice that their son has large calf muscles.
Pseudohypertrophy is a sign of muscle disease rather than a indication of good strength. There are some boys with Duchenne muscular dystrophy who have problems with delay in mental or language development. As a result the physical movement problems may be relatively less obvious in the early stages. Some families seek medical advice because they recognise that their child has a problem. For others the problem has only come to light as a result of a school medical examination or because teachers noticed that the child does not run or perform physical activities as well as most of the other children in his class.