Progressive multifocal leukoencephalopathy (PML): clinical and pathological findings in two short-duration patients.

The clinical features and neuropathological findings of two patients suffering from progressive multifocal leukoencephalopathy (PML) are reported. These patients had cancer and died two months and one month after onset of their neurological symptoms, respectively. In both demyelination was discovered only as a result of autopsy due to different reasons: the CAT-scan findings were misinterpreted in the first patient, while in the second diagnosis was overshadowed by the sudden progress towards a fatal outcome preceded by myoclonus and other encephalitis-like manifestations. The major findings were the extreme paucity of the mesodermal elements on the one hand, and the modest spread of the affected areas on the other. It is pointed out that, whatever the size of the lesions, characters were the same and that their formation could hardly be traced in time. The intriguing similarities between PML and several types of demyelination obtained experimentally using certain virus strains are remarked.