Progressive multifocal leukoencephalopathy in multiple myeloma associated with daratumumab, lenalidomide, and dexamethasone

Progressive multifocal leukoencephalopathy is a rare but fatal demyelinating disease of the central nervous system with reactivation of JC virus. Herein, we describe a case of progressive multifocal leukoencephalopathy associated with a therapeutic regimen of daratumumab, lenalidomide, and dexamethasone for multiple myeloma. A 69‐year‐old man with multiple myeloma was admitted to the neurological care unit due to progressive cognitive dysfunction after seven cycles of the regimen. His CD4+ T cell count was 190 cells/μL. Diffusion‐weighted magnetic resonance imaging revealed nodular diffusion restrictions in the frontal and parietal lobes. He was diagnosed with progressive multifocal leukoencephalopathy following a positive polymerase chain reaction test for JC virus DNA in the cerebrospinal fluid. After cessation of multiple myeloma treatment, his cognition and magnetic resonance imaging findings improved within 3 months. We should recognize this potentially fatal complication in patients receiving this regimen.