BK virus-associated progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is associated with the polyomavirus JC virus, while BK virus is causative of polyomavirus-associated nephropathy. We report the first definitive case of BK virus-associated PML. This case highlights the importance of biopsy for aetiologic diagnosis in the setting of viral latency and the absence of clear T-cell dysfunction or biologic therapy.

A 71-year-old woman with a low-grade B-cell non-Hodgkin lymphoma was referred by her haematologist for investigation of a 2-week history of progressive apraxia and right-sided neglect. Her past medical history also included Sjögren syndrome and hypogammaglobulinaemia. Her non-Hodgkin lymphoma was complicated by bone marrow infiltration, low-grade lymphadenopathy and splenomegaly. She had received oral chlorambucil 3 years before, but had not been on any therapy for the past 18 months as her disease was stable. She was receiving 6-weekly immunoglobulin infusions at the time of admission.