Cystic multiglandular maternal hyperparathyroidism diagnosed by neonatal hypocalcemic seizures

A 7-day-old male infant born to a healthy 33-year-old female at 37 weeks of gestation was brought to the local emergency department (ED) with sudden-onset tonic-clonic seizures. Laboratory testing revealed extreme hypocalcemia (ionized calcium of 3.2 mg/dl) and undetectable parathyroid hormone (PTH <10 pg/ml). Concomitant evaluation of the mother revealed both elevated ionized calcium (5.9 mg/dl) and PTH (116 pg/ml). The mother underwent preoperative ultrasound localization and sestamibi scan, followed promptly by parathyroidectomy. Given the cystic appearance and presence of multiglandular disease, evaluation for familial cystic parathyroid adenomatosis (hyperparathyroidism-jaw bone-tumor syndrome) and MEN 1 were undertaken. The infant was stabilized and discharged home. He returned to the ED with seizures at 1 month of age. After increasing calcium supplementation appropriately, he was monitored with weekly office visits. This represents a unique case of undiagnosed maternal primary hyperparathyroidism manifesting with intrauterine parathyroid suppression and hypocalcemic seizures in the newborn.