Progressive multifocal leukoencephalopathy associated with elranatamab therapy in relapsed/refractory multiple myeloma.
Tansuhan Çetiner, Merve Çağla Bilek, Selin Arslan Kirezli et al.
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Case in brief
A 67-year-old woman with relapsed/refractory multiple myeloma achieved a complete response with elranatamab, a BCMA- and CD3-targeting bispecific antibody. After her seventh treatment cycle, she developed dysarthria and gait disturbance. Brain MRI showed multifocal, non-enhancing white-matter lesions, and cerebrospinal fluid PCR detected JC virus, confirming progressive multifocal leukoencephalopathy (PML). Elranatamab was stopped, and she received intravenous immunoglobulin, mirtazapine, and compassionate-use nivolumab. Her neurological condition nevertheless worsened, requiring intubation and intensive care.
What made this case unusual
PML was diagnosed during elranatamab therapy, with MRI showing multifocal, non-enhancing white-matter lesions and CSF PCR confirming JC virus. The authors describe a probable association, with prior cumulative immunosuppression and treatment-related plasma-cell depletion and hypogammaglobulinemia as possible contributors.
Diagnostic / clinical pearl
In patients receiving BCMA-directed T-cell-redirecting therapy, new or unexplained neurological symptoms warrant consideration of PML; MRI and CSF JC virus testing established the diagnosis in this case.
Why it matters
The case adds a potential delayed neuroinfectious complication to the evolving safety profile of elranatamab and supports pharmacovigilance for PML during BCMA-targeted therapy.