|Boys with DMD often have enlarged calf muscles.|
Children with Duchenne muscular dystrophy (DMD) are often late walkers.
In toddlers, parents may notice enlarged calf muscles (see image at right). This enlargement is known as pseudohypertrophy, or "false enlargement," because the muscle tissue is abnormal and may contain scar tissue.
A preschooler with DMD may seem clumsy and fall often. Parents also may note that children have trouble climbing stairs, getting up from the floor or running.
By school age, children may walk on their toes or the balls of their feet with a slightly waddling gait, and fall frequently. To try to keep their balance, they may stick out their bellies and pull back their shoulders. Children also have difficulty raising their arms.
Many children with DMD begin using a wheelchair sometime between ages 7 and 12. Transition to a wheelchair usually is a gradual process; at first, the chair may be required only to conserve the child's energy when covering long distances. (Children often experience renewed independence once they fully transition to a power wheelchair.)
In the teen years, activities involving the arms, legs or trunk may require assistance or mechanical support.
Because of weakened leg muscles, boys with DMD have a distinctive way of rising from the floor, called a Gowers’ maneuver.
They first get on hands and knees, then elevate the posterior, then “walk” their hands up the legs to raise the upper body.
The muscle deterioration in Duchenne MD isn’t usually painful in itself. Some people report muscle cramps at times; these usually can be treated with over-the-counter pain relievers.
Because muscular dystrophy doesn’t affect nerves directly, touch and other senses are normal, as is control over the smooth, or involuntary, muscles of the bladder and bowel, and sexual functions.
Lack of dystrophin can weaken the muscle layer in the heart (myocardium), resulting in a condition called cardiomyopathy. Over time, sometimes as early as the teen years, the damage done by DMD to the heart can become life-threatening. The heart should be monitored closely, usually by a pediatric cardiologist. See Medical Management for more on cardiomyopathy in DMD.
Beginning at about 10 years of age, the diaphragm and other muscles that operate the lungs may weaken, making the lungs less effective at moving air in and out. Although the child may not complain of shortness of breath, problems that indicate poor respiratory function include headaches, mental dullness, difficulty concentrating or staying awake, and nightmares.
Weakened respiratory muscles make it difficult to cough, leading to increased risk of serious respiratory infection. A simple cold can quickly progress to pneumonia. It's important to get flu shots, and when infections occur, to get prompt treatment. See Medical Management for more on respiratory care in DMD.
About a third of boys with DMD have some degree of learning disability, although few have serious mental retardation. Doctors believe that dystrophin abnormalities in the brain may have subtle effects on cognition and behavior. Learning problems in DMD occur in three general areas: attention focusing, verbal learning and memory, and emotional interaction.
Children suspected of having a learning disability can be evaluated by a developmental or pediatric neuropsychologist through the school system’s special education department or with a referral from the MDA clinic.
If a learning disability is diagnosed, educational and psychological interventions can begin right away. The specialist may prescribe exercises and techniques that can help improve these areas, and the school also can provide special help with learning. See Medical Management for more about learning disabilities in DMD.