Functional parathyroid cyst and hypocalciuric hypercalcemia.

Parathyroid cysts are uncommon. They can be divided into functional and nonfunctional cysts depending on whether or not they are associated with hypercalcemia. Functioning cysts are very rare, with fewer than twenty reported cases. We report a case of functioning parathyroid cyst associated with hypocalciuric hypercalcemia. We have been unable to find a similar case previously reported in the literature.