A Project of the New Mexico AIDS Education and Training Center. Partially funded by the National Library of Medicine
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Fact Sheet Number 516
WHAT IS PML?
Progressive multifocal leucoencepha-
lopathy is a serious viral infection of the
“Encephalo” means brain.
means disease. Encephalopathy is a
disease of the brain. “Leuco-” means
disease of the white matter of the brain.
“Progressive” means that this disease
gets worse in a short time. “Multifocal”
means that it shows up in several
places at the same time.
Researchers estimate that about 6% of
people with AIDS develop PML. Most
cases of PML show up in people with
CD4 cell counts below 100. The exact
rate is hard to know because PML is
difficult to diagnose.
Most cases of PML used to be fatal.
People diagnosed with PML lived an
average of 6 months, and most died
within 2 years. However, if people with
PML start taking strong antiretroviral
medications (ARVs) to control their HIV,
they can survive much longer. Now
only about half of people with HIV and
PML die from PML.
The “JC” virus causes PML. Between
80–85% of all adults are exposed to this
In people with
weakened immune systems, JC virus
can become active.
first symptoms of PML are
weakness or coordination problems in
an arm or leg. There may be difficulty
thinking or speaking. Vision and
headaches can occur.
These symptoms can also occur with
other opportunistic infections, including
toxoplasmosis, lymphoma, inner ear
infections, or cryptococcal meningitis. It
is important to rule out these other
PML can be diagnosed using a scan of
the brain by magnetic
imaging (MRI). Another way to test for