Is progressive multifocal leukoencephalopathy associated with intrathecal IgG synthesis?

Examination of the cerebrospinal fluid by isoelectric focusing was done in 2 cases of progressive multifocal leukoencephalopathy (PML). The diagnosis was confirmed at autopsy in one case. IgG oligoclonal bands were found in both, suggesting that there was intrathecal immunoglobulin synthesis. Production may be due to a specific intrathecal response to papova virus or to IgG oligoclonal formation by lymphoma cells confined to the central nervous system or to a specific immune response to tumor cell antigens.