Progressive multifocal leukoencephalopathy as the first presentation of an underlying lymphoproliferative disorder.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating central nervous system disease caused by John Cunningham virus (JCV) reactivation in immunosuppressed patients. Although classically associated with advanced HIV infection, PML also occurs in patients with hematological malignancies, organ transplants, or on immunomodulatory therapies. The mortality rate can be high, ranging from 20 to 90%, depending on the underlying condition. Clinical presentation is variable, depending on the site of brain involvement, and diagnosis requires integration of clinical, radiological, pathological, and virological findings [1, 2, 3, 4]. We present the case of a 69-year-old HIV-negative woman with progressive neurological decline, whose initial workup focused on a suspected lymphoproliferative disorder. This case demonstrates the classical neuroimaging and neuropathological features of PML.