Hypercalcaemia in cerebellar medulloblastoma: pathogenesis of solid tumour-associated hypercalcaemia

A 7-year-old boy developed acute, severe hypercalcaemia following the partial excision of a cerebellar medulloblastoma. The serum calcium level was extremely high (19.8 mg/100 ml), but a skeletal survey revealed no apparent bone metastatic lesions; such lesions were only detected by X-ray 3 weeks after the onset of hypercalcaemia. Hypercalcaemia was promptly resolved by intravenous mithramycin administration, before which the serum parathyroid hormone level, 1,25-(OH)2-vitamin D level and the nephrogenous cyclic AMP level were low. However, the relation between serum calcium levels and urinary calcium excretions indicated that renal calcium reabsorption was increased in association with hypercalcaemia, suggesting that a parathyroid hormone-like effect was operative on the renal tubules. It is possible that a combination of increased bone resorption by metastatic tumour cells and renal tubular handling of calcium presumably mediated by tumour-produced humoral factors was responsible for the acute development of severe hypercalcaemia in this patient with medulloblastoma.