Progressive multifocal leukoencephalopathy(PML) is a fatal demyelinating disease that occurs in immunocompromised
hosts. We report a case of PML that developed in patient with T cell lymphoma of head and neck.
During chemotherapy for lymphoma, she was confused and had memory impairment. A magnetic resonance
imaging of the brain revealed confluent signal change at white matter of the frontal lobe, insula, and anterior limb
and genu of internal capsule. The lesion was confirmed with brain biopsy and the histopathological finding was
compatible with PML.