NCMP-09. SPONTANEOUS RESOLUTION OF PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY (PML) DEVELOPED AFTER RITUXIMAB TREATMENT FOR LOW-GRADE B-CELL LYMPHOMA

Abstract Progressive multifocal leukoencephalopathy (PML) is a rare viral infection caused by the reactivation of the JC virus, which causes significant morbidity and mortality. Rituximab, a CD20 inhibitor used for B-cell neoplasms as well as autoimmune diseases, is associated with the development of PML. Here, we report a case of a 74-year-old woman with a history of low-grade B-cell lymphoma with biopsy-proven PML with spontaneous immune reconstitution with clinical and radiographic improvement. For her low-grade B-cell lymphoma, she received six cycles of rituximab and bendamustine, followed by one cycle of maintenance rituximab, which was discontinued due to intolerance. Ten months later, she developed progressive left-sided paresthesias, paresis, and incoordination. Brain MRI revealed a large right subcortical frontal-parietal FLAIR hyperintense and peripherally enhancing lesion with leading-edge diffusion restriction. CSF studies revealed elevated protein (385 mg/dL) and negative JCV PCR. A brain biopsy was performed with tissue staining positive for SV40, consistent with PML. Her CD4 count was 88 cells/mm3. A repeat CSF sample one month later showed near normalization CSF protein (47 mg/dL) and negative CSF JCV PCR. MRI of the brain one month later demonstrated complete enhancement resolution and decreased FLAIR abnormality, which correlated with subjective and objective clinical improvement. Her serum CD4 also increased to 134 cells/mm3. This highlights a rare case of PML related to rituximab with spontaneous improvement, which may help guide clinicians in counseling patients who may also develop this complication. Furthermore, this supports the biological rationale for continued investigation of T-cell therapies to achieve immune reconstitution.