The use of cinacalcet hinders the diagnosis of parathyroid carcinoma in a chronic dialysis patient: a case report

Secondary hyperparathyroidism (SHPT) is a common complication in patients receiving chronic dialysis therapy. Although cinacalcet can control parathyroid function and bone turnover, preventing ectopic calcification remains challenging. Cinacalcet can also suppress PTH secretion due to parathyroid carcinoma in the same way as it does for parathyroid hyperplasia in the uremic condition. We present a case of parathyroid carcinoma partially controlled by cinacalcet, in which tumorous calcinosis was successfully resolved by total parathyroidectomy.

A female patient in her forties who had received dialysis for 12 years was referred to our hospital for painful ectopic calcifications on her right hip joint and both knees. Although she had been treated with alfacalcidol and cinacalcet for 2 years, this therapy had been discontinued 6 months earlier as a result of hypercalcemia. The patient exhibited normocalcemia (2.37 mmol/L) and hyperphosphatemia (2.42 mmol/L) with elevated intact parathyroid hormone (707,000 μg/L). Ultrasonography revealed an enlarged parathyroid gland on the left lower side of the thyroid gland. The otolaryngologist surgeons had to perform an en bloc excision to remove this parathyroid gland because of tight adhesions. Histological examination revealed that parathyroid cells had invaded the surrounding skeletal muscle through fibrous capsules, consistent with parathyroid carcinoma. Her joint pain disappeared 2 weeks after parathyroidectomy, and the tumorous calcinosis had largely resolved after 1 year.

Parathyroid carcinoma is a rare cause of hyperparathyroidism in end-stage kidney disease. Our case indicates that the use of cinacalcet hinders the diagnosis of parathyroid carcinoma in a chronic dialysis patient. When uncontrolled hypercalcemia and/or hyperphosphathemia develop during cinacalcet administration, parathyroidectomy should be considered to prevent a vicious exacerbation of ectopic calcification.