Recurrent Spontaneous Tumor Lysis Syndrome in Undiagnosed Follicular T-Cell Lymphoma.

Introduction: Spontaneous tumor lysis syndrome (TLS) is a rare, life-threatening metabolic complication that typically occurs in malignancies with high tumor burden. Early recognition is critical, even in the absence of a known malignancy, to prevent severe outcomes. Case Presentation: We report the case of an 89-year-old male with a history of chronic kidney disease, hyperparathyroidism, and myasthenia gravis, who experienced three episodes of TLS within 1 month. Initially, his metabolic disturbances were misattributed to dehydration. During his second admission, imaging revealed extensive lymphadenopathy, and a lymph node biopsy confirmed follicular helper T-cell lymphoma before his third hospitalization. Despite aggressive treatment, he developed metabolic encephalopathy and lost his decision-making capacity, while his family declined palliative care discussions. Conclusion: This case highlights the importance of considering TLS in patients with unexplained hyperkalemia, hyperuricemia, and hyperphosphatemia, even in the absence of a malignancy diagnosis. Early diagnosis and multidisciplinary care are essential to improve outcomes.