Progressive multifocal leukoencephalopathy presenting as a single mass lesion.

Progressive multifocal leukoencephalopathy (PML) consisting anatomopathologically of multiple foci of white matter demyelination may present both clinically and at CT scanning as a single mass lesion. An additional similar case is reported. As antiviral therapy may prove useful, characteristics of additional examinations including CT scan are described to promote an early diagnosis.