LAUSR

Tumor lysis syndrome (TLS) is an oncologic emergency characterized by metabolic derangements (e.g., hyperkalemia, hyperphosphatemia, hypocalcemia, and hyperuricemia) and clinical complications (e.g., renal failure, cardiac arrhythmia, new-onset seizure). It most often occurs in the setting of large tumor burden, specifically when rapidly dividing, chemosensitive cancer cells are treated with cytoreductive therapy. Rarely, spontaneous TLS can occur in the absence of cytotoxic therapy in patients with massive tumor burden. We present a patient who was admitted with B symptoms and confusion and was found to have hyperuricemia, hyperkalemia, and markedly elevated lactate dehydrogenase concerning for spontaneous TLS. Initial whole-body CT imaging was negative but subsequent workup including PET-CT and bone marrow biopsy confirmed the diagnosis of intravascular large B-cell lymphoma (IVLBCL) with significant bone marrow involvement. This case highlights that diagnosis of IVLBCL can be challenging and should be considered in patients presenting with fever of unknown origin, neurological symptoms and signs, and laboratory abnormalities suggestive of spontaneous TLS. Prompt recognition is paramount since appropriate management can improve renal parameters and the use of R-CHOP along with CNS prophylaxis using methotrexate can lead to durable response. Finally, we present an algorithm summarizing our approach to diagnosing and managing TLS. This article is protected by copyright. All rights reserved.