ESPE Abstracts

Neonatal severe hyperparathyroidism (NSHPT) is a rare autosomal recessive disorder due to inactivating mutations of calcium-sensing receptor. These receptors are vital in calcium homeostasis and are expressed in a number of tissues such as parathyroid glands, renal tubules and bone. Homozygous mutations lead to severe hypercalcemia and life-threatening bone demineralization if untreated. A neonate born to 2^nd degree consanguineous parents presented with poor feeding and low-grade fever at day 10 of life. At presentation, he had 30% weight loss and moderate dehydration. He was lethargic and hypotonic. His perinatal period was uncomplicated. A negative septic screen prompted evaluation for electrolyte abnormalities, which revealed an albumin-corrected calcium (Ca) of 7.4 mmol/L (normal: 2.2–2.7 mmol/L). Further, serum phosphate was low and alkaline phosphatase normal. In the absence of subcutaneous fat necrosis, and a typical presentation, NSHPT was clinically suspected, which was supported by an elevated PTH (403 pg/ml, normal 4–72 pg/ml) and radiological evidence of periosteal erosions. Family screening revealed normocalcemia and normocalciuria. Immediate management involved hyper-hydration and intravenous furosemide, following which Ca dropped to 6.8 mmol/L. Calcium dropped dramatically to 4.8 mmol/L after the administration of 0.75 mg/kg intravenous pamidronate in divided doses. At 6 weeks of age, Cinacalcet was started at 5 mg daily due to persistent hypercalcemia and gradually increased to 20 mg bid (12 mg/kg/d). There was negligible response to cinacalcet and a 2^nd dose of pamidronate was required. Due to symptomatic severe hypercalcemia, total parathyroidectomy with re-implantation of half a gland under the left biceps muscle was performed at 3 months of age. Perioperative frozen sections helped to identify the parathyroid glands. Histology revealed parathyroid hyperplasia. Intravenous calcium was started during the perioperative period. Calcitriol and calcium carbonate was added once oral feeds were commenced. Preoperative PTH was 1744 pg/ml and post-op PTH on D1 was undetectable. One month after surgery PTH had increased to 9 pg/ml and regular PTH testing showed a steady increase. Calcium supplements were gradually tailed off and omitted 6 months after surgery. Twelve months after surgery PTH is 34 pg/ml and there is no evidence of hyperplasia of the re-implanted gland. The 16-month infant is currently having normal growth and neurodevelopment without the need for any medications. This case of NSHPT awaits genetic confirmation. NSHPT is a rare cause of a common neonatal presentation. It can be fatal if not promptly recognized and treated.