Neonatal Severe Hyperparathyroidism Causing Life-Threatening Hypercalcemia Treated With Medical and Surgical Management.

A 3-day-old male presented to a peripheral remote hospital in New South Wales, Australia, with tachypnea. He was found to have hypercalcemia, with ionized calcium >2.5 mmol/L (>10 mg/dL) (0.97-1.5 mmol/L or 1.14-1.3 mg/dL) and serum calcium of 3.85 mmol/L (15.43 mg/dL) (2.2-2.8 mmol/L or 8.5-10.5 mg/dL). Peak serum calcium was 5.4 mmol/L (21.64 mg/dL). He was transferred to a tertiary pediatric intensive care unit. Medical management (including hyperhydration, diuretics, corticosteroids, bisphosphonates, cinacalcet, and calcitonin) failed to maintain normocalcemia; therefore, total parathyroidectomy was performed on day 16 of life. Hungry bones syndrome developed postoperatively, requiring high doses of calcium, calcitriol, and phosphate supplementation. Genetic testing identified compound heterozygosity for 2 likely pathogenic variants in the calcium-sensing receptor gene. He is now 3 years old and is growing and developing without any concerns. This case highlights the importance of aggressive initial management in addressing severe hypercalcemia through perioperative management principles as well as the prolonged nature of hungry bones syndrome.