Leiomyoblastoma associated with intractable hypercalcemia and elevated 1,25-dihydroxycholecalciferol levels. Treatment by hepatic enzyme induction.

A 42-year-old woman, with a previously resected jejunal leiomyoblastoma, was first seen with liver metastases 31/2 years after the tumor resection. Intractable malignant hypercalcemia appeared eight months later, together with renal insufficiency. No osteolytic lesions were detected. Levels of parathyroid hormone, cyclic adenosine monophosphate, and 1,25-dihydroxycholecalciferol (1,25[OH]2D) were not useful in distinguishing between the hypercalcemia of malignancy and concurrent hyperparathyroidism. Despite renal insufficiency, hypercalcemia, and subtotal parathyroidectomy, the 1,25(OH)2D levels remained elevated, consistent with the speculation that a tumor product stimulated 1-alpha-hydroxylation of 25-hydroxycholecalciferol. Phenytoin and phenobarbital (enzyme induction therapy), in combination with phosphorus and glucocorticoids, appeared to be useful in controlling the hypercalcemia.