Description
Albeit increased serum CK level and abnormal muscle histology are always present, boys with DMD are phenotipically indistinguishable from the normal ones at birth and, in their first years of life, acquire early motor milestones at normal times. A clear defect in muscle function becomes generally apparent by the end of the second year. As the disease is typically diagnosed between the ages of 3 and 7, the first two years are often considered and referred to as clinically presymptomatic.