Abstract
Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease triggered by the reactivation of JC virus (JCV) in individuals with immunodeficiency, particularly those with untreated human immunodeficiency virus (HIV) infection. This case report describes a 46-year-old HIV-positive man who initially presented with neurological symptoms and was incorrectly diagnosed as cerebral infarction. Although standard real-time polymerase chain reaction (PCR) testing for JCV in cerebrospinal fluid (CSF) at a commercial laboratory was negative, neuroimaging and clinical suspicion prompted ultrasensitive PCR testing at a national laboratory. This test detected a low viral load of JCV (28 copies/mL), confirming the diagnosis of PML. The patient underwent treatment with antiretroviral therapy and corticosteroids to prevent immune reconstitution inflammatory syndrome; however, his neurological symptoms persisted. This case highlights the importance of ultrasensitive CSF JCV testing for early PML diagnosis when standard PCR tests are inconclusive, particularly in HIV patients with atypically low JCV levels. It also highlights the diagnostic challenges of PML and emphasizes the clinical value of advanced PCR techniques for timely and accurate diagnosis in similar cases.