Endocrine Abstracts

Giant-cell tumor is a skeletal disorder that occurs secondarily to hyperparathyroidism and is caused by long-term stimulation of parathyroid hormone (PTH) excess. The overactivity and proliferation of osteoclasts stimulated by PTH breaks down bone and leads to replacement of bone matrix and thinning of the cortex. True giant-cell tumor is a rare jaw osteolytic benign tumor belonging to the larger family of giant-cell tumors.

We report the case of a 47 years old female patient without significant personal history. The patient was referred to us for hyperparathyroidism after being operated in maxillofacial surgery department for a right mandibular tumor progressing from 1 year associated with muscle cramps and fatigue. The pathology exam found a giant-cell tumor. Blood exams showed: PTH=81.5 pg/ml, Serum Calcium=2.5 mmol/l, serum phosphorus=1.3 mmol/l and creatinine=63 mmol/l. Cervical ultrasound showed a left lower pole parathyroid adenoma. The para- thyroid scintigraphy showed no parathyroid or ectopic tumor. No other bone lesions were found on bone scintigraphy. Since the calcium rate was normal (2.5 mmol/l), we investigated the 25 (OH) Vitamin D3 level. Our patient had a vitamin D deficiency.

Thus the diagnosis was a secondary hyperparathyroidism caused by a vitamin D deficiency associated to a giant cell tumor. The jaw tumor syndrome was eliminated due to the lack of hyperparathyroidism in the family history and to the absence of uterine fibroids and renal cysts in our patient.

This case illustrates the simultaneous combination of a mandibular giant cell tumor and a normocalcemic hyperparathyroidism. The vitamin D dosage rectified the diagnosis.