Unusual hypocalcaemia in breast cancer relapse with multiple bone metastasis

[摘要] Severe hypocalcaemia in breast cancer with bone metastasis is a rare finding usually associated with an advanced stage ofthe disease. We report a case of a 45-year-old woman with a history of local ductal carcinoma in situ (DCIS) of the breast,who presented with muscle tremors and general weakness. Hypocalcaemia was evident, with a positive Chvostek sign anda serum calcium level of 5.9 mg/dL (1.47 mmol/L), phosphorus 5.9 mg/dL (normal range: 2.3–4.7 mg/dL) with normal levelsof albumin, magnesium and parathyroid hormone. High oral doses of alpha calcitriol and calcium with i.v. infusion ofhigh calcium doses were instituted, altogether sufficient to maintain only mild hypocalcaemia. A whole-body CT revealedbone lesions along the axial skeleton. A biopsy from a bone lesion revealed a metastasis of breast carcinoma. With thispathological finding, leuprolide (GNRH analogue) and chlorambucil (alkylating agent) were initiated, followed by prompttapering of infused calcium down to full discontinuation. Serum calcium was kept stable close to the low normal range byhigh doses of oral alpha calcitriol and calcium. This course raises suspicion that breast metastases to the skeleton causedtumour-induced hypocalcaemia by a unique mechanism. We assume that hypocalcaemia in this case was promoted by acombination of hypoparathyroidism and bone metastasis.

[学科分类] 血液学