Profound hypophosphatemia in a multiple myeloma patient receiving zoledronic acid, cyclophosphamide and furosemide

Hypophosphatemia is a rare occurrence in multiple myeloma patients due to compromised renal function. We describe a male patient who presented with acute renal failure, anemia, hypercalcemia, hyperphosphatemia, and was diagnosed with Stage IIIB IgG kappa multiple myeloma. He subsequently developed profound hypophosphatemia during the course of his treatment, which included zoledronic acid, cyclophosphamide, and furosemide. A combination of the phosphate depleting effect of the three drugs and his improving renal function may have contributed to the profound hypophosphatemia.