We report the case of a 28 year-old female with cystic bone lesions, discovered after a minimal trauma fracture, and subsequent diagnosis of severe primary hyperparathyroidism. The patient was admitted with a corrected calcium of 3.74 mmol/L (2.10-2.60) and a PTH of 168pmol/L (1.6-7.2). There was a history of progressive pelvic pain and fatigue. The patient’s grandmother also had hypercalcaemia. Imaging confirmed a large parathyroid mass (4.8 x 1.9 x 1.9cm) and multiple expansive lesions throughout the axial and appendicular skeleton consistent with osteitis fibrosa cystica. Management was with IV bisphosphonates and parathyroidectomy by en bloc resection, given concerns of parathyroid malignancy. Histology was consistent with an atypical adenoma. Parafibromin staining was positive. Post-operative hungry bones syndrome required large doses of calcium and calcitriol.
Pre-operative diagnosis of parathyroid malignancy remains difficult and there is a paucity of guidelines to stratify risk. Resultant indequate surgical intervention causes increased morbidity and mortality1. Patients with high pre-operative clinical suspicion for malignancy must be managed via oncologic resection to avoid recurrence. FNA is avoided as there is a risk of parathyromatosis2. Clinical red-flags include grossly elevated corrected calcium and PTH, end organ manifestations and a large parathyroid gland with suspicious features. The presence of large tumours (>3cm) with a corrected calcium >3.0mmol/L has a PPV of malignancy of 99.8%3.
Given the lack of reliable of histology, evaluation with parafibromin immunohistochemistry is essential in atypical parathyroid lesions. Loss of parafibromin reactivity strongly predicts parathyroid malignancy4. Furthermore a panel including PGP9.5, galectin-3 and Ki67 appears superior to individual immunostain5. Genetic testing for HRPT2 and MEN-1 germline mutations should be considered.6 Hyperparathyroidism jaw tumour syndrome, an autosomal dominant condition due to HRPT2 mutation, is associated with significantly higher risk of parathyroid carcinoma. This results from a loss of expression of parafibromin, a tumour suppressor protein involved in transcriptional pathway7,8.