PARATHYROID CARCINOMA PRESENTING AS PRIMARY HYPERPARATHYROIDISM IN ADOLESCENCE

Abstract

INTRODUCTION/BACKGROUND
Parathyroid carcinoma is an extremely rare cause of primary hyperparathyroidism in adolescence. Despite being malignant in nature, the diagnosis if often delayed and is already severe at presentation.

CASE
We present a 16-year-old male with background of delayed developmental milestones presenting with recurrent seizures. On physical examination, there were no syndromic features, bony deformities or neurological deficits. Laboratory examination revealed severe hypercalcaemia (3.64 mmol/L), low serum phosphate (0.4 mmol/L), elevated serum ALP (2121 U/L), normal range for 16-yearold male: 68-430 U/L) and a normal renal profile. Serum intact parathyroid hormone (iPTH) was elevated (186 pg/ ml, normal range: 15-57 pg/ml). The 25-hydroxy vitamin D was normal (75.59 nmol/L). Thyroid function test was also normal. Ultrasound of the neck revealed a hypoechoic lesion posterior to the right thyroid gland measuring1.6 x 2.5 x 2.9 cm. Neck CT confirmed an enlarged right parathyroid gland measuring 1.9 x 3.0 x 2.6 cm with no evidence of adjacent organ infiltration. The 99mTechnetium (Tc) sestamibi scan was not performed due to patient’s poor cooperation. Hypercalcaemia was managed with intravenous saline, iv pamidronate 90 mg and sc denosumab 60 mg. He underwent right parathyroidectomy and hemithyroidectomy with central lymph node dissection. Intra-operatively, the right inferior parathyroid was grossly enlarged and adhered to the right thyroid lobe and distal part of the right recurrent laryngeal nerve. Histopathology examination of the parathyroid gland confirmed a nodular mass weighing 5 g and measuring 30x28x9 mm with central cervical lymph node infiltration. The cytomorphological features with increased mitotic activity (11 per 50 hpf) and the presence of vascular invasion strongly favoured the diagnosis of parathyroid carcinoma. Post operatively, the course was complicated with hungry bone syndrome. At discharge, the patient’s iPTH and calcium level was reduced to 6.66 pg/ml and 2.20 mmol/L, respectively.

CONCLUSION
Size of parathyroid lesion, severe hypercalcaemia, significantly raised ALP and iPTH levels are clues to indicate parathyroid carcinoma as the cause of primary hyperparathyroidism.