Hypercalcemic hyperparathyroidism in hypophosphatemic rickets

A 25-year-old white woman with sporadic hypophosphatemic rickets presented with a 7 year history of chronic mild hypercalcemia, osteitis fibrosa cystica and hypercalcemic nephropathy. Serum immunoreactive parathyroid hormone was elevated by greater than 100-fold and a 3.5 g parathyroid tumor was found at operation. Survey of the literature reveals that of 9 previous cases in which hypercalcemic hyperparathyroidism occurred in association with hypophosphatemic rickets, only two had classical x-linked familial hypophosphatemic rickets. It appears more than likely that this unusual combination of skeletal diseases represents the chance occurrence of primary hyperparathyroidism in patients with underlying x-linked familial hypophosphatemic rickets rather than a complication of phosphate therapy.