Hypercalcemia induced by metastatic bone cancer in a patient with chronic renal failure

We present a diagnostically challenging case of hypercalcemia in a 50-year-old Japanese woman with chronic renal failure due to chronic interstitial nephritis. She had a history of a radical mastectomy for breast cancer at the age of 30. Despite her chronic renal failure, serum levels of calcium and alkaline phosphatase were abnormally high, and levels of intact parathyroid hormone and of parathyroid hormone-related protein were undetectable on repeated assays. Bone scintigram revealed multiple hot lesions in the ribs, which were suggestive of bone metastases of breast cancer. After treatment with tamoxifen citrate was initiated, her serum calcium levels returned to the normal range and hot lesions were no longer evident on bone scintigraphy in 14 months. Thus, our patient's hypercalcemia was considered to be related to bone metastases of breast cancer. Physicians should be aware of existence of malignancy in the patient with chronic renal failure and hypercalcemia.