"Paramyxovirus-like" intranuclear inclusions occurring in the nervous system in diverse unrelated conditions.

Filamentous intranuclear inclusions similar to the "paramyxovirus-like" intranuclear inclusions described in active multiple sclerosis (MS) were observed incidentally in four patients who had diverse disorders such as rabies, mannosidosis, metachromatic leukodystrophy, cerebral aneurysm and ischemic infarcts. The observation is in support of the mounting evidence that the "virus-like" intranuclear inclusions are not specific for MS and may occur frequently in a variety of diverse conditions. Moreover, neither virological nor immunological evidence as to the viral nature of the intranuclear inclusions has been presented to date, and the intranuclear inclusions have been observed mostly in degenerating or autolyzed cells in biopsied or autopsied tissue samples. In view of all the circumstantial evidence, it is suggested that the intranuclear "paramyxovirus-like" inclusions may represent an alternation of nuclear chromatin common to antemortem degeneration and postmortem autolysis in a variety of cells, the nature of which remains to be elucidated.