Pseudohyperparathyroidism secondary to gigantic mammary hypertrophy.

Pseudohyperparathyroidism encompasses both ectopic hyperparathyroidism and the more commonly encountered nonparathyroid humoral hypercalcemia of malignancy--metastatic breast cancer being the classic example. Benign breast disease is a rare cause of hypercalcemia. We recently managed a patient with gigantic mammary hypertrophy that occurred during pregnancy who concomitantly manifested marked nonparathyroid hypercalcemia. This report strongly suggests that a casual relationship exists between benign breast disease and hypercalcemia.