PML, or Progressive Multifocal Leukoencephalopathy, is a rare and often fatal disease that affects the central nervous system. As with most medical conditions, there are several synonyms or alternative names that healthcare professionals may use to refer to PML. Some of the most common synonyms for PML include multifocal leukoencephalopathy, JC virus encephalopathy, and PMLE. Other less frequently used terms include subacute multifocal encephalopathy, demyelinating leukoencephalopathy, and multifocal progressive leukoencephalopathy. Regardless of the name used, PML is a serious condition that requires prompt medical attention and treatment to improve the patient's prognosis and overall quality of life.