Supplementary Material for: Eosinophilic pleocytosis in the cerebrospinal fluid following CAR-T cell therapy for CNS lymphoma: A case for warning?

Introduction: CAR-T cell therapy, emerging as an efficient treatment option for patients with secondary central nervous system (CNS) lymphoma, is frequently complicated with immune effector cell-associated neurotoxicity syndrome (ICANS). Case Presentation: We report a case of a 64-year-old woman with transformed follicular lymphoma, developing high-grade ICANS with eosinophilic pleocytosis following third-line therapy with CAR-T cells (tisagenlecleucel). During bridging therapy, she declined neurologically and was diagnosed with secondary CNS lymphoma. She received methotrexate-cytarabine-thiotepa-rituximab regimen with clinical and radiological improvement. Post-CAR-T cell infusion she developed cytokine release syndrome grade II and ICANS grade III. Given the lack of response to steroids, anakinra was initiated with complete ICANS resolution. Cerebrospinal fluid (CSF) analysis, performed only on day +10 due to thrombocytopenia, revealed eosinophils, while infections were excluded. Conclusion: This report emphasizes the importance of CSF analysis in individuals with CAR-T-related neurotoxicity for elucidating the role of specific immune cells in such complications.