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Duchenne muscular dystrophy: Sx

Duchenne’s Muscular Dystrophy (DMD) is an x-linked recessive disease involving a mutation of the protein dystrophin. Dystrophin is found in skeletal, cardiac, and smooth muscle as well is in the brain, therefore manifestations follow suit. The disease manifests in males typically by age four and is characterized by progressive weakness of proximal muscle groups. Affected patients often will not start walking until 18 months or later. They may be observed to have a waddling gait, fall easily, and have difficulty climbing stairs. DMD patients may also have difficulty standing from a seated position requiring the use both arms to stand (Gower maneuver). The disease is progressive and many children are unable to walk by age 11. Some may develop thoracolumbar scoliosis. Pseudohypertrophy of the calves is common and is found in 60% of patients. Macroglossia is present in approximately 30% of patients.

DMD is also associated with intellectual impairment. Cardiac manifestations typically do not appear in early stages of the disease although patients can develop dilated cardiomyopathy. EKGs may show sinus tachycardia, tall R waves in the right precordial leads, left precordial Q waves, or inverted T waves. Echocardiography may be normal or show wall motion abnormalities. Pulmonary manifestations are due to effects of the disease on the muscles of expiration initially then progresses to include the muscles of inspiration. Respiratory failure is common by age 20.