Progressive multifocal leukoencephalopathy: simultaneous detection of JCV DNA and anti‐JCV antibodies in the cerebrospinal fluid

We report on a case of biopsy-proven progressive multifocal leukoencephalopathy (PML) in a patient without obvious immunodeficiency. Analysis of the cerebrospinal fluid revealed the simultaneous presence of JC virus DNA and of locally produced, anti-JC virus antibodies. The intrathecal humoral immune response increased throughout the course of the disease, whereas the detection of the JC genome became ultimately negative in spite of the continuous extension of the lesions with fatal outcome.