Progressive Multifocal Leukoencephalopathies (PML) is a rare and debilitating neurological disorder that affects the central nervous system. This condition is characterized by the progressive destruction of myelin, the protective covering of nerve cells in the brain. While PML is a specific term used in medical contexts, there are several synonyms that can be used interchangeably to refer to this ailment. These include "progressive multifocal leukoencephalopathy", "PML disease", "multifocal leukoencephalopathy", and "progressive white matter disease". Although each term slightly varies in its wording, they all describe the same disorder that poses significant challenges to patients and requires specialized medical care.