ABSTRACT
A cystic parathyroid adenoma is rare. A case of primary hyperparathyroidism, with the cystic formation of a parathyroid adenoma and a severe bony lesion, is reported. A 52-year-old male was admitted due to pain in both hips and for evaluation of hypercalcemia. The plasma level of the intact parathyroid hormone(iPTH) was elevated to 1424pg/mL. Ultrasonography and the computed tomography revealed a parathyroid cyst on the left thyroid lower pole. Parathyroid scintigraphy detected a parathyroid adenoma. A radiograph showed a subperiosteal bone resorption on the phalanges, and a brown tumor(osteitis fibrosa cystica) on the femur shaft was noted. A surgical excision of the parathyroid adenoma was performed. The PTH level in the cystic fluid was increased. A histological examination confirmed a cystic parathyroid adenoma. The PTH level was normalized after the operation.