Hyperparathyroidism due to primary cystic parathyroid hyperplasia.

Cysts of the parathyroid glands are uncommon, and functioning parathyroid cysts that cause primary hyperparathyroidism are rare. A 63-year-old man had primary hyperparathyroidism because of cystic hyperplasia of all four parathyroid glands. He also had squamous cell carcinoma of the soft palate, chronic renal failure, hypertension, type-4 renal tubular acidosis, a hyperplastic thyroid adenoma, and hyporeninemic hypoaldosteronism. To our knowledge, this is the first patient to be described with hyperparathyroidism due to multiple parathyroid cysts. The finding of cystic involvement of all four glands supports the theory that at least some parathyroid cysts are either a result of a common embryologic defect or of retention of parathyoid secretions rather than of cystic infarction of parathyroid adenomas.