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An entity which is related to progressive

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multifocal leukoencephalopathy is IRIS,

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Immune Reconstitution Inflammatory Syndrome.

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This is an entity that has been largely

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described at Johns Hopkins, my host institution,

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where we had a large AIDS population.

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We often gave the HAART therapy,

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and yet we saw patients who had PML,

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who got dramatically worse

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once the HAART therapy was instituted.

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This is the description of IRIS.

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It's the use of combined antiretroviral therapy,

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which markedly improves immune function

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and prognosis in HIV patients.

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However,

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the PML dramatically worsens with the highly

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active antiretroviral therapy,

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despite the recovery of the immune system.

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And this is the immune reconstitution

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inflammatory syndrome,

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known as IRIS.

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What do you see on your MR scans

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in patients who have IRIS?

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What you see is PML that dramatically worsens

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in its severity, may show necrosis,

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may show contrast enhancement,

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may show increasing mass effect,

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despite the reinstitution of the patient's immune system

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through the HAART therapy.

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This is an example of a patient who had IRIS.

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These are three FLAIR scans,

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as well as the postgadolinium T1-weighted scan.

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So you see that there are multiple lesions in

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the white matter extending to the subcortical

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U fibers on this example.

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So once again,

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deep involvement to the subcortical

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U fibers of PML.

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You see involvement of the corpus callosum.

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You see this confluent area

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in the left parietal lobe,

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as well as in the frontal lobes,

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as well as in the posterior fossa.

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All of this is good for PML.

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However,

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on the postgadolinium enhanced scans,

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this looks like a much more angry disease.

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You see areas of abnormal enhancement,

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which would be unusual for PML.

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You see areas that appear to show

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necrosis or marked edema,

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low signal intensity on the T1-weighted scan,

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centrally within these areas of demyelination.

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So an aggressive immune response

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leading to dramatic dropout of the white matter

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in a pattern that looks like it's actually

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necrotic centrally.

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And you have this wild contrast enhancement pattern,

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which is very atypical for PML.

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It usually does not happen.

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And instead,

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this is likely the response to the

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institution of HAART therapy

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leading to Immune Reconstitution

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Inflammatory Syndrome, or IRIS.