All nerves are affected, but disproportionately so. The nerves in the legs are affected first and most severely.
Symptoms usually begin between mid-childhood and early adulthood.
The exact cause is unknown. The disorder is inherited, with both dominant and recessive inheritance patterns. The disorder most commonly affects the nerve cells to the feet and legs, most significantly the peroneal nerve. The damage is slowly progressive, usually beginning with foot drop and progressing up the legs. There is a loss of muscle control, loss of muscle tone, and eventual loss of muscle mass caused by lack of nervous stimulation to the muscles.