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BK virus-associated progressive multifocal leukoencephalopathy

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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.

Clinical record

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.

On examination, the patient had right upper-limb drift and incoordination, with normal power, reflexes and tone throughout. She had difficulty following three-step commands, and had paraphasia and constructional apraxia. She did not have palpable lymphadenopathy but had an enlarged spleen 10 cm…