Symptoms
Symptoms usually appear before age 6 and may appear as early as infancy. They may include:
Fatigue
Learning difficulties (the IQ can be below 75)
Intellectual disability (possible, but does not get worse 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
Trouble getting up from a lying position or climbing stairs
Weakness quickly gets worse
Progressive difficulty walking
Ability to walk may be lost by age 12, and the child will have to use a wheelchair
Breathing difficulties and heart disease usually start by age 20