A CASE OF ACUTE LYMPHOBLASTIC-LEUKEMIA ACCOMPANIED WITH THE PRODUCTION OF PARATHYROID HORMONE-RELATED PROTEIN

Hypercalcemia accompanied with malignant tumors is generally classifie d into two categories, namely with or without bone metastasis. As for the latter, bone resorption-stimulating factors produced by tumor cell s, such as parathyroid hormone-related protein (PTHrP), show hormone-l ike effects and promote a bone resorption. Many cases have been report ed regarding the production of PTHrP in adult T cell leukemia (ATL), b ut few have been reported with acute lymphoblastic leukemia (ALL). We report here a similar case with ALL. A 12-year-old male presented with fever, petechiae and thrombocytopenia, and was diagnosed as ALL. We s tarted the induction therapy and confirmed complete remission. Later, he relapsed 3 times without symptoms apart from hypercalcemia at the b eginning. Elevation of the serum calcium level followed by a rise of l ymphoblastic cells was recognized. Bone metastasis was excluded since bone mineral density and serum mid region PTH were normal and no abnor mal findings were noticed on X rays and Tc-99m bone scintigraphy. Howe ver, his urinary PTHrP level was high, and his lymphoblastic cells sta ining immunocytochemically with the monoclonal antibodies against the C-terminal region of PTHrP showed a positively brownish color. Finally , he died of pulmonary aspergillosis. Hypercalcemia was not related to serum PTH or bone metastasis. ATL viral infection reported as a cause of PTHrP production was also excluded from several experimental data. Therefore, we concluded that lymphoblastic cells directly produced PT HrP, and that this PTHrP played an important role in the induction of hypercalcemia.