Progressive Multifocal Leukoencephalopathy (PML) is a life-threatening brain infection that can occur in people living with HIV. It is caused by a virus - the JC virus. "JC" are the initials of the first patient to be diagnosed with PML. The virus is the polyomavirus, a family of viruses that also includes human papillomavirus (HPV).
The "progressive" term in PML means that it continues to get worse and usually leads to severe brain damage. The term "multifocal" means that the virus "JC" cause diseases in various parts of the brain. The "leukoencephalopathy" means that the disease affects the white matter of the brain. More specifically, the JC virus infects cells in the brain calls oligodendrocytes. These cells are responsible for producing myelin, a fatty substance that helps protect the nerves in the brain. If too much myelin is lost and not replaced by oligodendrocytes, the nerves are damaged and often stop working correctly.
More than 85% of adults worldwide are infected with the JC virus, usually during the early years of childhood. However, the virus becomes active only in people who have the functioning of the immune system down. This includes people undergoing immunosuppressive chemotherapy for cancer and people with compromised immune systems due to HIV. Before the use of combination antiretroviral therapy (ART), it was estimated that between 3 and 7 percent of people with AIDS developed PML. It usually occurs in people with very low CD4 cell count (less than 100), but was seen in some HIV-infected persons with CD4 500 cell count.
In the early years of the AIDS epidemic, the PML was often progressive and fatal. Death occurred between 1 and 4 months after the onset of symptoms. While the diagnosis of PML today remains rapid in progression and possibly fatal, improvements in our ability to stabilize the immune system using HIV drugs have helped improve the prognosis associated with this opportunistic infection.
PML symptoms include mental deterioration, loss of vision, speech disorders, ataxia (inability to coordinate movements), paralysis, and coma. In rare cases, seizures can occur. As injuries and nerve damage can occur in any part of the brain, the first symptoms may be different among people with the disease.
Translation into Portuguese of Brazil:Rodrigo S. Pellegrini