Transient Hypercalcemia in Preterm Infants

reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access page A premature male infant was born after 31 weeks gestation with birth weight of 1705 g. He was the first baby of nonrelated Ashkenazi Jewish parents. There was no history of inherited, genetic, or metabolic disorders in the whole family except for nephrolithiasis in the mother's family. On admission to the neonatal intensive care unit he was given parenteral nutrition. Enteral feeds were started on day of life (DOL) 2. Parenteral nutrition was discontinued at DOL 7. Full enteral feeds of mother's milk were achieved on DOL 10, when routine vitamin D supplementation of 400 IU/day was started. Cow's milk–based powdered human milk fortifier (Similac, Ross/Abbott-Promedico) was added from DOL 11. Hypercalcemia was first detected on DOL 16 when total calcium levels went up to 13.6 mg/dL (normal range for term newborn levels = 8-11.3) while ionized calcium levels were also high (5.8-5.9 mg/dL on DOL 19-46) with highest levels of 6.07 mg/dL measured on DOL 28. Laboratory evaluation as well as treatment was initiated (Table 1). Total serum calcium levels normalized on DOL 64 with 10.5 mg/dL, and urine calcium/creatinine ratio dropped to 1.07 mg/mg only on DOL 72, resolving to normal infant range of 0.5 mg/mg on DOL 87. With oral supple-mentation phosphorus levels gradually increased up to 6.2 mg/dL on DOL 87. Follow-up renal ultrasound on DOL 80 showed that only one small calculus was left in the lower pole of the left kidney. Routine vitamin D supplementation (400 IU/day) was restarted at DOL 80 because of chemical rickets with rising alkaline phos-phatase levels (up to 991 IU/L) despite phosphorus sup-plementation, 1,25(OH) 2 D levels dropped to normal range (60 pg/mL) and low 25(OH)D levels (14.9 ng/ mL). Alkaline phosphatase levels started to decrease, and hypercalcemia or hypercalciuria did not reappear, suggesting transient infantile hypercalcemia as the most likely diagnosis. Oral phosphate supplementation was discontinued after a month, and the baby maintained normal serum phosphorus levels. At the age of 11 months, the calcium level was 10.1 mg/dLl, phosphorus 6.8 mg/dL, alkaline phosphatase 269 IU/L, parathyroid hormone (PTH) 17 pg/mL, 25(OH)D 41.9 ng/mL, 1,25(OH) 2 D 60 pg/mL, and urine calcium/creatinine ratio 0.5 (mg/mg). Vitamin D supplementation was discontinued at the age of 18 months. The boy, more than 2 years old, has …