Hypercalcemia-Driven Spontaneous Tumor Lysis Syndrome in a Case of Recently Diagnosed Multiple Myeloma: An Unusual Clinical Encounter.

Tumor lysis syndrome (TLS) represents an oncological emergency characterized by the rapid disintegration of neoplastic cells and subsequent release of their intracellular content into the systemic circulation due to cytotoxic therapy. However, a rare variant, spontaneous TLS (STLS), can occur without an evident precipitating factor. Prompt recognition of high-risk individuals and initiation of prophylactic interventions are crucial to forestall complications of electrolyte imbalance, such as cardiac arrhythmias or sudden death. We present the case of a 74-year-old male who was referred to the hematologist/oncologist's office after exhibiting pelvic pain, progressive weakness, fatigue, unintended weight loss over the last five months, and an imaging study revealing osteolytic lesions suggestive of a malignant condition. Initial diagnostic assessment revealed a kappa-light-restricted multiple myeloma, hypercalcemia, hyperuricemia, hyperphosphatemia, and elevated creatinine, diagnosing STLS. This case illustrates an uncommon presentation of STLS and malignant hypercalcemia in the setting of multiple myeloma. We expound upon potential tumor- and patient-specific risk factors previously documented to precipitate STLS, correlate them with our case, and provide comprehensive insights into the diagnostic, therapeutic, and noteworthy educational aspects for clinicians.