Parathyroid Apoplexy Following Cinacalcet Treatment in Primary Hyperparathyroidism

Abstract

Cinacalcet, a calcimimetic drug, is considered a safe and valid option for the treatment of hypercalcemia in patients with primary hyperparathyroidism who are unable to undergo parathyroidectomy. Hypocalcemia and gastrointestinal adverse reactions are the main side effects reported in patients treated with cinacalcet. We present here the case of an 80-years-old patient with primary hyperparathyroidism treated with cinacalcet for 17 months who developed a severe and symptomatic episode of hypocalcemia requiring hospitalization 1 month after reaching a daily dose of 180 mg. Follow-up laboratory and imaging exams showed remission of primary hyperparathyroidism and disappearance of the parathyroid adenoma, suggesting a possible association between cinacalcet therapy and parathyroid infarction resulting in normalization of the elevated serum parathyroid hormone levels and severe hypocalcemia. No known cases of iatrogenic parathyroid apoplexy have thus far been described. We report here the first case of parathyroid apoplexy associated with the administration of cinacalcet in a patient with primary hyperparathyroidism. Parathyroid apoplexy features heterogeneous clinical manifestations ranging from relatively asymptomatic to potentially life-threatening cases. The occurrence of this complication should be carefully considered in patients with primary hyperparathyroidism in therapy with cinacalcet.

Keywords: cinacalcet; hungry bone syndrome; hypocalcemia; parathyroid apoplexy; primary hyperparathyroidism.

Figure 1

Neck ultrasound and ^99mTc-sestamibi scintigraphy performed on admission and 8 months after parathyroid apoplexy. (A) Baseline neck ultrasound showed a solid and hypoechoic 8 mm nodule located behind the right thyroid lobe (arrow). (B) Baseline ^99mTc-sestamibi scintigraphy showed an area of increased uptake (arrow). (C) Follow-up neck ultrasound performed 8 months later notice the near complete disappearance of the nodule. (D) Follow-up ^99mTc-sestamibi scintigraphy performed 8 months later showing a marked reduction of the uptake, although residual activity was still noticeable.

Figure 2

Serum levels of total calcium and parathyroid hormone (PTH). The x-axis shows the calendar time and the boxes above the graph show the treatments. Assessments were made at several time points before, during and after cinacalcet treatment. Note the marked decline in PTH and total calcium (arrow) occurring about a month after cinacalcet reached the 180 mg/dl daily dosage.

Figure 3

Morphological appearance of the fine-needle aspirate of the patient's parathyroid nodule. Note the presence of necrotic debris and inflammatory cells mainly consisting in neutrophils (black arrow), macrophages (white arrow), and lymphocytes (arrowhead). Original magnification 20X.