[Progressive multifocal leukoencephalopathy: morphologic possibilities of diagnostic classification methods and in...

Progressive multifocal leucoencephalopathy is caused by infection with JC virus. The disease affects patients with immunodeficiencies, hematologic diseases, and patients treated with radiotherapy. The disease is characterised by foci of demyelinisation with atypical astrocytes and oligodendrocytes. Oligodendrocytes contain typical intranuclear inclusions. Progressive multifocal leucoencephalopathy and its verification is presented in three cases. Two patients died of progression of a malignant neoplasm and the leucoencephalopathy was a complication of the malignancy. The third case was a biopsy specimen taken from the brain of a patient who received a renal transplant. The material of all patients was analysed by light and electron microscopy, and in situ hybridisation with a probe specific for JC virus. In situ hybridisation proved to be the most specific and a simple method to demonstrate the infection in all cases. It is useful in instances in which the histologically detectable lesion is not characteristic, and in cells in which the conventional histologic methods fail to reveal the intranuclear inclusions of JC virus.