If a boy has typical findings of DMD and a defect is found in his dystrophin gene, the diagnosis is established. Most but not all doctors still advise that the diagnosis be further supported by a muscle biopsy to demonstrate lack of dystrophin as the ultimate proof of diagnosis. The increasing disability can be alleviated by such measures as physiotherapy, but it cannot be stopped. Recently the use of cortisone derivatives has been shown to slow the progress of DMD but at the expense of side effects. As the ability to walk is lost, the function of the hands and arms becomes increasingly important in determining the affected person's abilities.
Most affected people survive into their twenties.
A small minority survive only to their late teens, another small number to more than 30 years of age. Some people with DMD have additional problems. These include impaired intellectual development and problems with joints, the spine, the heart and the lungs. Intellectual handicap is more frequent in boys with DMD than in the general population but only affects a proportion of boys. Unlike the muscle weakness, it is not progressive.