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Immune Reconstitution Inflammatory Syndrome (IRIS)


KEY FACTS

Terminology

  • I mmune R econstitution I nflammatory S yndrome (IRIS)

    • Atypical/worsening opportunistic infection

    • HIV/AIDS patients following commencement of HAART

    • Patients with MS, immunomodulatory therapy

Imaging

  • Progressive multifocal leukoencephalopathy (PML)-IRIS

    • White matter (WM) hypodensities with ↑ mass

    • Patchy atypical enhancement

  • TB-IRIS

    • ↑ leptomeningeal enhancement

    • ↑ size of ring-/nodular-enhancing tuberculomas

  • Crypto-IRIS

    • ↑ nodular meningeal/subependymal enhancement

    • ↑ in size of “gelatinous” pseudocysts

Top Differential Diagnoses

  • Diffuse/patchy WM abnormalities in AIDS

    • HIV encephalitis, PML, CMV infection

  • Focal/multifocal brain lesions in AIDS

    • Lymphoma, toxo, tuberculoma, cryptococcosis

Pathology

  • Reconstitution of immunity → abnormal immune response to infectious/noninfectious antigens

  • IRIS is not caused by relapse/recurrence of preexisting disease

Clinical Issues

  • 1/4 to 1/3 HIV-infected patients develop IRIS

  • PML, TB common IRIS-associated pathogens

Diagnostic Checklist

  • IRIS if worsening/enhancing lesions in

    • HIV patient who recently started HAART

    • MS patient on immunomodulatory therapy

Axial T1WI C+ MR in a patient with HIV and PML shows subtle hypodensity in right insular region
without any abnormal enhancement. FLAIR images (not shown) demonstrated multifocal confluent white matter hyperintensities.

Axial T1 C+ MR in the same patient after initiation of HAART therapy and significant clinical deterioration shows patchy nodular and linear foci of enhancement
and worsening of the underlying hypodensity
, findings typical for PML-IRIS.

Axial T1WI C+ MR demonstrates meningeal enhancement in the left sylvian fissure
in an HIV-positive patient with tuberculous meningitis.

Axial T1WI C+ MR in the same case shows worsening of imaging appearance after placement on HAART. There is an increase in enhancement, which appears more nodular
, and there is development of surrounding edema
. This worsening of disease could be due to drug resistance; however, the time course after starting HAART makes IRIS most likely.

TERMINOLOGY

Abbreviations

  • Immune reconstitution inflammatory syndrome (IRIS)

Synonyms

  • Immune restoration disease (IRD)

  • Immune restitution syndrome (IRS)

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