Supplementary Material for: 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 one 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.