(See also general discussion of hypercalcemia.)
The most common cause of neonatal hypercalcemia is
Iatrogenic causes usually involve excess calcium or vitamin D, or phosphate deprivation, which can result from prolonged feeding with incorrectly prepared formula.
Other causes of neonatal hypercalcemia include
Maternal hypoparathyroidism or maternal hypocalcemia may cause secondary fetal hyperparathyroidism, with changes in fetal mineralization (eg, osteopenia).
Subcutaneous fat necrosis may occur after major trauma and causes hypercalcemia that usually resolves spontaneously.
Neonatal hyperparathyroidism is very rare.
Williams syndrome's key features include supravalvular aortic stenosis, pulmonary valvular or peripheral pulmonary artery stenosis, atrial septal defect and/or ventricular septal defect, renal artery stenosis, aortic anomalies, elfin facies, and hypercalcemia of unknown pathophysiology; infants may also be small for gestational age, and hypercalcemia can be noted early in infancy, usually resolving by age 12 mo.
Idiopathic neonatal hypercalcemia is a diagnosis of exclusion and is difficult to differentiate from Williams syndrome and often requires genetic testing.
Symptoms and signs of neonatal hypercalcemia may be noted when total serum calcium is > 12 mg/dL (> 3 mmol/L). These signs can include anorexia, gastroesophageal reflux, nausea, vomiting, lethargy or seizures or generalized irritability, and hypertension. Other symptoms and signs include constipation, abdominal pain, dehydration, feeding intolerance, and failure to thrive. Some neonates have weakness. With subcutaneous fat necrosis, firm purple nodules may be observed on trunk, buttocks, or legs.
Marked elevation of serum calcium may be treated with normal saline 20 mL/kg IV plus furosemide 2 mg/kg IV and, when persistent, with corticosteroids and calcitonin. Bisphosphonates are also increasingly used in this context (eg, etidronate by mouth or pamidronate IV). Treatment of subcutaneous fat necrosis is with a low-calcium formula; fluids, furosemide, calcitonin, and corticosteroids are used as indicated by the degree of hypercalcemia. Fetal hypercalcemia caused by maternal hypoparathyroidism can be treated expectantly, because it usually resolves spontaneously within a few weeks. Treatment of chronic conditions includes a low-calcium, low-vitamin D formula.