Poster Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

A 66-year-old man was admitted with severe PTH-dependent hypercalcaemia (ionised calcium 2.77mmol/L, PTH 181pmol/L) and non-oliguric acute kidney injury (eGFR 13mL/min/1.73m²) on a background of stage II chronic kidney disease without known parathyroid disease. Further investigation revealed a sestamibi and FDG-avid 43x26x39mm neck mass arising from the right thyroid lobe, suspected to invade the oesophagus and right recurrent laryngeal nerve. Widespread permeative bony changes were present raising concern for metastatic disease. However, neither sestamibi nor supraphysiological FDG-avidity were demonstrated, and multiple myeloma was excluded. A diagnosis of osteitis fibrosa cystica was supported by archetypal changes on bilateral hand X-ray (Figure 1). Normocalcaemia was achieved pre-operatively with intravenous fluids, zoledronic acid and calcitonin. Neck exploration identified a large parathyroid tumour with atypical cytological and architectural features, preserved parafibromin staining on immunohistochemistry, and no locoregional invasion. Genetic testing did not demonstrate germline variants. The final diagnosis was thus a sporadic atypical parathyroid tumour. The PTH level declined to a day-1 post-operative nadir of 31.4pmol/L. Persistent PTH elevation was attributed to renal failure, zoledronic acid effect, vitamin D deficiency and calcium-sensing receptor down-regulation in the remaining parathyroid glands from prolonged severe hypercalcaemia. The postoperative course was complicated by hungry bone syndrome (nadir ionised calcium 0.6mmol/L on day 8), responsive to intravenous calcium, and calcitriol up to 2microg BD. The renal function improved by hospital discharge (eGFR 36mL/min/1.73m²).

Our case highlights the potential for aggressive atypical parathyroid tumours to mimic parathyroid cancer and widespread metastatic disease. No guidelines distinguish osteitis fibrosa cystica from skeletal metastases. Our evaluation, utilising FDG-PET and sestamibi-uptake, ascertained the potential for surgical cure. The complexities of perioperative management in parathyroid crisis are also addressed including urgent calcium-lowering therapy to support early parathyroidectomy, measures to prevent hungry bone syndrome and the management of this complication.