Hypercalcemia associated with chronic lymphocytic leukemia.

A patient with chronic lymphocytic leukemia (CLL) is described in whom hypercalcemia occurred in association with elevation of the peripheral lymphocyte count and expansion of total tumor mass. Hypercalcemia was ameliorated with the institution of chemotherapy for the leukemic process and subsequent fall in WBC count and decrease in total tumor burden; hypercalcemia recurred with relapse of the leukemic process. The serum immunoreactive parathyroid hormone (iPTH) concentration, when measured, was inappropriately elevated for the degree of hypercalcemia. The hypercalcemia would appear to be a direct consequence of the leukemia, and possibly involved secretion of a parathyroid hormone-like polypeptide by the CLL cells. Although a possible role for either an osteoclast-activating substance or prostaglandins was not excluded, they would not account for the elevated serum iPTH levels observed.