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Fingolimod-associated PML — SCE Neurology MCQ

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ModerateMSFingolimod-associated PMLSCE Neurology

A 48-year-old man presented with progressive cognitive decline and hemianopia while receiving fingolimod. On examination, there was lymphopenia and subtle left-sided neglect. Initial investigations showed: MRI showed enlarging subcortical white-matter lesions without mass effect; CSF JC virus PCR was positive. What is the most likely underlying mechanism?

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Correct answer: B — JC virus lytic infection of oligodendrocytes

JC virus lytic infection of oligodendrocytes is the best answer because the vignette describes Fingolimod-associated PML: progressive deficits with JC PCR in an immunosuppressed patient indicate PML. Prion protein misfolding is plausible in a neighbouring presentation, but the chronology, examination or investigation pattern does not match the key discriminator here. Alpha-synuclein neurodegeneration and Small-vessel lipohyalinosis are less appropriate because they would require different localisation, timing or test findings; Large-vessel thromboembolism would fit a different syndrome. Clinical pearl: MS relapse is usually more acute and often enhances.

Reference: NICE NG220; ABN guidance on disease-modifying therapies for MS