PML is a very serious illness that can be fatal. It’s caused by a virus called the JC virus. Most adults carry it, and it usually doesn’t cause any health problems. But it can if you have a weak immune system — if your body’s natural defenses against illness aren’t working right.

Does PML cause death?

In general, PML has a mortality rate of 30-50 percent in the first few months following diagnosis but depends on the severity of the underlying disease and treatment received. Those who survive PML can be left with severe neurological disabilities.

Has anyone ever survived PML?

We identified 24 PML patients who survived more than 5 years from disease onset. Among them, 22 (92%) were men and 2 (8%) women. The mean age at onset of PML was 38 years (range 31–54 years). The predisposing condition in all patients was HIV infection, except one who had non-Hodgkin’s lymphoma (Patient #6, table 1).

The term “progressive” in PML means that the disease continues to get worse and often leads to serious brain damage. The term “multifocal” means that JCV causes disease in multiple parts of the brain. However, it is possible for an individual with PML to have only one brain lesion instead of several lesions.