By Shishido-Hara, Yukiko Higuchi, Kayoko; Ohara, Sinji; Duyckaerts, Charles; Hauw, Jean-Jacques; Uchihara, Toshiki Abstract Progressive multifocal leukoencephalopathy is a fatal demyelinating disorder due to human polyomavirus JC infection in which there are viral inclusions in enlarged nuclei of infected oligodendrocytes.