Progressive multifocal leukoencephalopathy post ibrutinib therapy in relapsed chronic lymphocytic leukaemia

Progressive multifocal leukoencephalopathy (PML) is a generally fatal infection of the cerebrum by the JC virus. It occurs in a range of primary and secondary immunosuppressed states and has become more common with AIDS and increasing the use of immunosuppressive therapies. Recently, Ibrutinib, a Bruton's Tyrosine Kinase Inhibitor (BTKi), has also been associated with PML. Here, we describe the case of a 77-year-old man treated for relapsed Chronic Lymphocytic Leukemia (CLL) with Ibrutinib, who eventually developed a fatal cerebellar granule cell variant of PML confirmed on autopsy. The case adds to the growing body of literature finding such an association with BTKis and highlights the importance of clinical vigilance in patients receiving such therapy.