[Ectopic production of calcitriol by non-Hodgkin lymphoma as a cause of hypercalcemic crisis].

HISTORY AND ADMISSION FINDINGS: A 92-year-old woman was admitted because her general condition had deteriorated during the last two weeks and acute kidney injury had developed. Moreover, she suffered from periods of disorientation and confusion while heretofore she was autonomous. INVESTIGATION, TREATMENT AND COURSE: Clinical and biochemical evaluation revealed a hypercalcemic crisis with markedly increased serum levels of calcium (3.77 mmol/l; reference values 2.2-2.65), an acute kidney injury and neuropsychiatric disturbances. Ultrasound scan and magnetic resonance imaging of a palpable mass in the right abdomen showed a tumor in the retroperitoneal space. Histological evaluation specified the tumor as non-Hodgkin lymphoma. Further investigation revealed no other reason for the hypercalcemia but enhanced levels of calcitriol. Since serum levels of calcidiol were increased while levels of calcidiol were normal, we assumed ectopic production of calcitriol by non-Hodgkin lymphoma as the cause of hypercalcemic crises. This could been proven by the decrease of calcium and calcitriol levels during the course of lymphoma treatment.

CONCLUSION: Hypercalcemia of malignancy is the most common cause of hypercalcemia in the inpatient setting. The evaluation of these cases should consider ectopic production of calcitriol a cause of hypercalcemia.