In 1958, Åström, Mancall, and Richardson described a demyelinating disease distinct from multiple sclerosis and other demyelinating disorders which they called progressive multifocal leukoencephalopathy.1 The condition is characterized by progressive and fatal neurologic deterioration with "dementia, alterations in the state of consciousness, language disorders, visual impairment and evidence of pyramidal tract involvement."1 Pathologically, the brain shows widespread focal destruction of myelin sheaths in all gradations of size and states of evolution with relative sparing of the axis cylinders. "These foci have shown a pronounced tendency to become confluent so that large plaquelike lesions may occur. Associated with the myelin destruction is a distinctive cytological reaction consisting of hypertrophy of astrocytes into bizarre gigantic forms and alteration of oligodendrocytes with the production of large, round, densely basophilic nuclei."1 Recently, Richardson reviewed the subject and accepted a total of 24 cases as progressive multi focal leukoencephalopathy. The additional material
JOHNSTON RF, GREEN RA, HEADINGTON JT. Progressive Multifocal Leukoencephalopathy. Arch Intern Med. 1963;111(3):353–362. doi:10.1001/archinte.1963.03620270079013
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