Adult Refsum Disease (ARD) is the most treatable of the leukodystrophies because phytanic acid is not produced by the body, but is only found in foods. With treatment, muscle weakness, numbness, and dry and scaly skin generally disappear. However, vision and hearing problems may persist and the sense of smell may not return. Untreated, ARD can lead to death caused by heartbeat abnormalities.
This answer is based upon information from the National Institute of Neurological Disorders and Stroke.