PML, or Progressive Multifocal Leukoencephalopathy, is a rare and serious brain infection caused by the JC virus. This virus is typically harmless in healthy individuals but can become active in those with weakened immune systems, such as people with HIV/AIDS or those undergoing certain treatments for cancer or autoimmune diseases. The symptoms of PML can include confusion, weakness, and vision problems, which may worsen over time. Diagnosis often involves brain imaging and testing for the JC virus. Unfortunately, there is currently no specific treatment for PML, making early detection and management of underlying conditions crucial.