PML-IRIS — SCE Neurology MCQ

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HardMultiple Sclerosis & CNS InflammationPML-IRISSCE Neurology

A 55-year-old woman with MS on natalizumab develops PML. After stopping natalizumab and PLEX, she worsens 3 weeks later with new MRI enhancement. What is the cause?

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Correct answer: B — Immune reconstitution inflammatory syndrome (IRIS)

PML-IRIS occurs when immune reconstitution after natalizumab cessation causes exaggerated inflammation against JC virus-infected tissue. New MRI enhancement (unlike non-enhancing PML) is characteristic. Management may include high-dose corticosteroids. A: MS relapse has different pattern. C: New PML is non-enhancing. D: Stroke has vascular territory distribution. E: Rebound causes MS activity, not PML worsening.

Reference: ABN MS Guidelines (2022); Wattjes PML Protocol