Progressive Multifocal Leukoencephalopathy: A Case Report

Progressive Multifocal Leukoencephalopathy (PML) is a demyelinating disease that severely affects the central nervous system (CNS) through the JC polyomavirus. In most of the population, this DNA virus remains latent; however, in patients with profound immunosuppression, such as those with HIV, the virus can become reactivated. Replication under these conditions may lead to viral genome rearrangements that produce neurotropic variants capable of replicating in glial cells and inducing the lysis of oligodendrocytes – the myelin-producing cells of the CNS. A 39-year-old male patient from Caxias do Sul, RS, previously healthy, former alcohol and tobacco user, sought neurological evaluation in November 2024 due to sudden bilateral visual loss, altered mental status, and progressive headache. Cranial magnetic resonance imaging (MRI) revealed abnormalities in the left parieto-occipital region associated with encephalomalacia, suggestive of PML. Rapid tests for HIV and syphilis, as well as serologies for hepatitis B and C, were initially negative. For further clarification, cerebrospinal fluid (CSF) analysis showed a predominance of mononuclear leukocytes (97%), elevated protein levels (89 mg/dL), glucose of 84 mg/dL, and lactate of 1.8 mmol/L. Additional cervical and cranial MRIs, along with abdominal computed tomography (CT), were performed to rule out other diseases and identify the etiology, together with a Western blot test.The patient was later evaluated by an infectious disease specialist in May 2025, when HIV infection was confirmed by polymerase chain reaction (PCR), showing a viral load of 1,240 copies/mL and a CD4 T-lymphocyte count of 71 cells/mm³. In the same month, antiretroviral therapy (ART) with tenofovir, lamivudine, and dolutegravir was initiated. Although PML is a progressive disease with high mortality, HIV diagnosis and timely ART initiation are essential to minimize neurological sequelae. Diagnostic suspicion should be raised in any patient presenting with subacute neurological deficits and evidence of immunosuppression. The investigation should include brain imaging, blood count, HIV serology, and viral load. If suggestive findings are present, CSF collection and PCR testing for JC virus can confirm the diagnosis. In conclusion, this case highlights the importance of early HIV diagnosis and immediate treatment initiation to prevent CD4 decline to levels that may allow the emergence of opportunistic infections such as PML.