Absence of imune deficiencies in a case of progressive multifocal leukoencephalopathy.

Progressive multifocal leukoencephalopathy (PML) is a rare disease related to a slow virus infection of the central nervous system; it is usually seen in patients who have impaired immunologic function. The present patient with biopsy-proved PML was found to have no demonstrable defects in either cellular or humoral immunity as assessed by multiple parameters. Thus, it appears that PML may occur in the presence of intact immune responses.