Hyperviscosity Syndrome, Hypercalcemia, and Acute Renal Failure as Initial Manifestations of Multiple Myeloma in an Octogenarian.

Background: Multiple myeloma (MM) is a hematological malignancy characterized by the proliferation of abnormal plasma cells, often accompanied by the excessive secretion of monoclonal immunoglobulins. Hyperviscosity syndrome (HVS) is a rare but life-threatening complication that leads to microcirculatory impairment and organ dysfunction. Additionally, hypercalcemia, commonly associated with osteolytic bone destruction, can further result in acute kidney injury and altered consciousness. Case Presentation: We describe an 80-year-old male who presented with confusion, generalized weakness, decreased urine output, and fever. He was subsequently diagnosed with MM complicated by HVS, hypercalcemia, and acute renal failure. Initial investigations revealed severe anemia, significantly elevated IgG levels (8612.26 mg/dL), multiple osteolytic lesions, and deteriorating renal function. The patient also exhibited epistaxis and neurological symptoms. Emergency plasmapheresis was initiated, alongside calcitonin and supportive therapy for hypercalcemia. Bone marrow examination confirmed plasma cell myeloma. Following five sessions of plasmapheresis, immunoglobulin levels decreased significantly, and clinical symptoms improved markedly. The patient was then successfully transitioned to immunomodulatory agents and systemic chemotherapy. Conclusion: MM presenting with HVS and hypercalcemia can be rapidly fatal. Early recognition and immediate intervention with plasmapheresis and supportive care are crucial for improving patient outcomes and facilitating subsequent oncological treatment.