Multiple sclerosis is a severe disease caused by progressive destruction of the myelin sheath in the central nervous system. The Guillain-Barré disease is due to destruction of the myelin sheath in the peripheral nervous system caused by autoimmunity (attack by the own immune system). The genetic deficiency in the formation or preservation of the myelin sheath is an X-linked inheritance called adrenoleukodystrophy. The movie “Lorenzo’s Oil” featured a boy with this disease and his father's dramatic search for treatment.