Suspecting neonatal severe primary hyperparathyroidism in late onset neonatal sepsis

Background: Neonatal severe primary hyperparathyroidism (NSPHPT) is disorder characterized by severe hypercalcemia and severe hyperparathyroidism resulting from a loss of function of the calcium-sensing receptor (CaSR), encoded by a gene located on the long arm of chromosome 3 (3q-13.3-21). It can be fatal if timely management is not initiated. Clinical Description: A 10-day-old exclusively breastfed girl presented with poor feeding, constipation, and lethargy for 2-3 days before admission. She was born of third-degree consanguinity to a primiparous woman with normal gestation. Born at term, with a birth weight of 3.1 kg, she was discharged uneventfully on day 3 of life. At admission, she was hemodynamically stable and normothermic but exhibited tachypnea, dehydrated with 15% weight loss as compared to birth weight, lethargy, and hypotonia. Salient investigations showed euglycemia, no dyselectrolytemia, and negative sepsis screen, but severe hypercalcemia and hyperparathyroidism. A final diagnosis of NSPHPT was made. Clinical exome sequencing showed homozygous CaSR gene frameshift mutation on chromosome 3. Management: Hypercalcemia was managed initially by standard protocol, including furosemide, hyperhydration, bisphosphonates, and cinacalcet. Subsequently, parathyroidectomy was performed at 2 months of age. Postoperatively, the infant is 5 months old and thriving well. Conclusion: NSPHPT should be considered in the presence of features of clinical sepsis, failure to timely regain birth weight, and a profile suggesting atypical calcium homeostasis.