Late onset progressive multifocal leukoencephalopathy in Hodgkin lymphoma.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease resulting from infection of oligodendrocytes in the central nervous system with John Cunningham virus. Although PML is commonly diagnosed in immunocompromised patients with human immunodeficiency virus, it can also arise in other immunodeficient states. In this report, we present an unusual case of PML occurring 40years after chemoradiation therapy for Hodgkin lymphoma in a patient with normal total lymphocyte counts on annual surveillance. Although current guidelines recommend annual complete blood counts for patients in remission, this testing may be insufficient to monitor patients with chronic CD4+ lymphopenia.