ABSTRACT
The acquired demyelinating diseases of the human central nervous system (CNS) are a heterogeneous group of disorders characterized by selective damage to myelin (reviewed in Raine, 1984; Lassmann, 1999; Wingerchuk and Weinshenker, 2008). The underlying cause of myelin loss may be infectious (e.g., progressive multifocal leukoencephalopathy, post-infectious encephalitis), or in¢ammatory/ immune mediated (multiple sclerosis, neuromyelitis optica), or may result from exposure to toxic factors, chronic ischemia of the deep white matter associated with aging, or nutritional de¡ciencies (vitamin B12 de¡ciency). It has also been postulated that iatrogenic autoimmune encephalomyelitis may have occurred following immunization with CNS homogenates, as, for example, when several patients treated with Pasteur’s vaccine for rabies developed encephalitis, polyneuritis, and perivascular demyelination (Baxter, 2007). In contrast to the acquired demyelinating diseases listed above, myelin diseases with a genetic basis usually develop early in life, display symmetric and extensive involvement of the hemispheric white matter, and are associated with widespread loss of AXONS and high morbidity.
