Problems are usually not evident until eighteen months to four years of age. On average a diagnosis is not made until the child is five, although with increasing awareness of the problem, some boys are diagnosed earlier. 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.