Symptoms usually appear before age 6 and may appear as early as infancy. They may include:

• Fatigue
• Mental retardation (possible, but does not worsen over time)
• Muscle weakness
  • Begins in the legs and pelvis, but also occurs less severely in the arms, neck, and other areas of the body
  • Difficulty with motor skills (running, hopping, jumping)
  • Frequent falls
  • Rapidly worsening weakness
• Progressive difficulty walking
  • Ability to walk may be lost by age 12

By age 10, the person may need braces for walking. By age 12, most patients are confined to a wheelchair.

A complete nervous system (neurological), heart, lung, and muscle exam may show:

• Abnormal heart muscle (cardiomyopathy)
• Congestive heart failure or irregular heart rhythm (arrhythmias) -- rare
• Deformities of the chest and back (scoliosis)
• Enlarged calf muscles, which are eventually replaced by fat and connective tissue (pseudohypertrophy)
• Loss of muscle mass (wasting)
• Muscle contractures in the heels, legs
• Muscle deformities
• Respiratory disorders, including pneumonia and aspiration of food or fluid into the lungs (in late stages of the disease)

Tests may include:

• Electromyography (EMG)
• Genetic tests
• Muscle biopsy
• Serum CPK