Progressive multifocal leukoencephalopathy during ixazomib-based chemotherapy

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disease of the central nervous system that most often affects immunocompromised individuals. It is caused by the reactivation of the John Cunningham virus (JCV), which is found in latent form in the majority of adults. We describe a 59-year-old man with multiple myeloma who developed severe neurological deficits during treatment with ixazomib-based chemotherapy. A diagnosis of PML was established with gadolinium-enhanced magnetic resonance imaging (MRI) and by detection of JCV in the cerebrospinal fluid. Despite cessation of chemotherapy and treatment with mirtazapine, he had an inexorable neurological decline and died two months after presenting to hospital. Multiple myeloma and its treatments can predispose patients to opportunistic infections including PML. Although there have been case reports of PML in patients with multiple myeloma treated with bortezomib (a different proteosome inhibitor), this is, to our knowledge, the first documented case of PML in a patient treated with a regimen that includes ixazomib.