Primary hyperparathyroidism is the most common cause of hypercalcemia. It is most commonly due to a single adenoma in 80-85% of cases, an atypical adenoma in 1.2-1.3%, and parathyroid carcinomas in <1%. Although atypical parathyroid adenomas make up 1-2% of primary hyperparathyroidism, there is limited knowledge about the pathophysiology, clinical presentations and significance of such a diagnosis.
A 91-year-old male with a background history of stable primary hyperparathyroidism presented with refractory symptomatic hypercalcemia. Despite having a long history of stable disease with parathyroid hormone (PTH) levels consistently around 30, he developed a sudden rise in PTH levels to 78, associated with the persistent hypercalcemia without major change in renal function. Following suboptimal calcium management with medical therapies, surgical resection was performed and pathology demonstrated features of an atypical parathyroid adenoma.
Post-operatively this patient had rapid correction of PTH and calcium levels. He was able to be discharged 7 days post operation with stable calcium levels.
This case highlights distinguishing features that can be used in clinical practice, that may suggest an atypical parathyroid adenoma and offers insight into the pathophysiology of atypical adenomas and the risk of developing parathyroid carcinoma.