Rickets of prematurity. Supranormal levels of serum 1,25-dihydroxyvitamin D
R. W. Chesney, A. J. Hamstra and H. F. DeLuca
Rickets, hypocalcemia, hypophosphatemia, and hyperparathyroidism were found
in a low-birth-weight premature infant. The concentration of plasma
calcitriol (1,25-dihydroxyvitamin D) was 145 pg/mL. With additional
exogenous calcitriol (37.5 ng/kg/24 hr) given for eight weeks, the
biochemical abnormalities were corrected and healing of rickets was
evident. Three months later, while receiving only 400 IU of ergocalciferal
daily, the patient had normal levels of serum calcium, phosphate, and
alkaline phosphatase with a serum calcitriol concentration of 36 pg/mL.
These observations suggest that rickets of prematurity may involve a
malabsorption of calcium and phosphorus with an elevated calcitriol level
needed to overcome this inadequate absorption. Additional doses of
calcitriol may be of benefit in these infants, although it must be given
carefully. Furthermore, the role of phosphate supplementation in these
infants requires consideration.
