Krabbe disease is a rare, incurable genetic disorder caused by a deficiency of an enzyme that is necessary for myelin metabolism. This can cause deterioration of the myelin sheath and death of brain cells. It affects both the central and peripheral nervous systems. Symptoms may appear during the first six months of life, during adolescence, or adulthood. (National Institute of Neurological Disorders and Stroke. NINDS Krabbe Disease Information Page. Accessed 2007.