Differential Diagnoses for Hypercalcemia, Acute Renal Failure, and New-Onset Anemia

Primary Differential Diagnoses

The American Society of Clinical Oncology recommends considering multiple myeloma as the leading diagnosis when hypercalcemia, renal failure, and anemia present together, characterized by the "CRAB" criteria: hypercalcemia, renal dysfunction, anemia, and bone lesions 1, 2
Hypercalcemia in multiple myeloma occurs through increased osteoclastic bone resorption mediated by the plasma cell clone, with a serum M-protein ≥3 g/dL and/or bone marrow clonal plasma cells ≥10% present with end-organ damage 1, 2
The International Myeloma Society suggests that anemia in multiple myeloma results from bone marrow infiltration by plasma cells and suppression of normal hematopoiesis 1, 2
The American College of Chest Physicians recommends considering squamous cell lung cancer with hypercalcemia of malignancy, as it occurs in 10-25% of lung cancer patients and is most common with squamous cell histology, with hypercalcemia developing through parathyroid hormone-related protein (PTHrP) production 3
The National Comprehensive Cancer Network states that median survival after discovery of hypercalcemia in lung cancer is approximately 1 month, making urgent diagnosis essential 3, 5
The European Society for Medical Oncology notes that renal failure in lung cancer results from hypercalcemia-induced volume depletion and decreased glomerular filtration 3, 6

The American Society of Clinical Oncology recommends a diagnostic approach including serum and urine protein electrophoresis with immunofixation, serum free light chain assay, bone marrow biopsy, and skeletal survey or whole-body CT to identify lytic lesions 1, 2
The American College of Chest Physicians suggests measuring serum intact PTH, PTHrP, 1,25-dihydroxyvitamin D, 25-hydroxyvitamin D, calcium, albumin, phosphorus, and magnesium to diagnose hypercalcemia of malignancy 3, 5
The National Comprehensive Cancer Network recommends immediate IV hydration with normal saline and bisphosphonates (zoledronic acid 4 mg IV over 15 minutes) for symptomatic or severe hypercalcemia (>14 mg/dL) regardless of underlying cause 7, 5