Intravascular large B-cell lymphoma presenting as encephalomyelitis diagnosed by renal biopsy: a case report.

Background: The assessment of patients with multifocal lesions in the brain and spinal cord is complicated. A comprehensive neurologic workup requires extensive imaging evaluation, lumbar puncture, and sometimes a stereotactic biopsy to identify the final diagnosis. We report a case of intravascular large B-cell lymphoma (IVLBCL) manifesting as encephalomyelitis, which was diagnosed via percutaneous renal biopsy. IVLBCL should be considered as a differential diagnosis in cases with brain and spinal cord involvement.

Case presentation: A 43-year-old man with no significant medical history presented with mild dysuresia and recurrent sudden-onset numbness of the right limbs over one month. Initial brain Magnetic Resonance Imaging (MRI) showed hyperintensities in the right frontal lobe, left parietal lobe, and bilateral centrum semiovale on diffusion-weighted images (DWI). He was diagnosed as cerebral embolism, but thrombolysis treatment was ineffective. Follow-up brain MRI revealed extension of the lesions and an intramedullary non-enhancing lesion was observed at the T1-T2 level on spinal cord MRI. Lumbar puncture was performed, and a diagnosis of inflammatory encephalomyelitis was considered. However, his symptoms worsened despite four months of glucocorticoid treatment. Subsequently, the patient underwent an ¹⁸F-FDG PET-CT scan. It showed diffuse increased FDG uptake in bilateral kidneys, but no specific increased FDG uptake was observed in the brain. To establish the final diagnosis, stereotactic brain biopsy was advised; however, the patient's poor general condition precluded this procedure. Instead, we conducted a percutaneous kidney biopsy due to the abnormality of kidneys on PET-CT. The final diagnosis was intravascular large B-cell lymphoma with predominant involvement of the kidneys, brain, and spinal cord. He was treated with five cycles of intravenous chemotherapy. His neurological symptoms recovered almost completely. Repeat MRIs of the brain and spinal cord demonstrated marked improvement.

Conclusions: This case highlights the importance of awareness of IVLBCL. It should be a differential diagnosis in cases with brain and spinal cord involvement. Early diagnosis is crucial for patient outcomes.