Severe hypercalcemia in a child with acute nonlymphocytic leukemia: the role of parathyroid hormone-related protein and proinflammatory cytokines.

Among the hematological malignancies, hypercalcemia has often been reported in lymphoid malignancies such as multiple myeloma and adult T cell leukemia/lymphoma, but it has only rarely been described in acute nonlymphocytic leukemia. We describe here a 14-month-old girl with acute monocytic leukemia complicated by severe hypercalcemia (4.6 mmol/l) at presentation. A bone survey showed generalized bone resorption, but no localized osteolytic lesions. A search for the etiology of the hypercalcemia revealed that the serum levels of parathyroid hormone-related protein (PTHrP) and also proinflammatory cytokines with stimulatory effects on osteolytic bone resorption - TNF-alpha, IL-6 and M-CSF - were elevated. The patient achieved complete remission with induction chemotherapy, and the levels of PTHrP and the cytokines became normalized. In this case, PTHrP and cytokines might have acted cooperatively to exacerbate bone resorption, resulting in severe hypercalcemia.