Rickets in a very low birth weight infant.

A report on a case of rickets in a very low birth weight infant (VLBWI) is presented. The infant had no high-risk factors for rickets and was fed a specialized preterm formula with vitamin D supplementation (200 IU daily) by 10 days of age. Feeds were advanced so that an enteral intake of 120 cal/kg/day was achieved by the 20th day of life. Mean calcium, phosphorus, and vitamin D intakes between the 20th and 61st days of life were 185 mg/kg/day, 93 mg/kg/day, and 367 IU/day, respectively. On the 62nd day of life, a diagnosis of rickets was made, and a nutrient balance study was performed. Urinary calcium excretion was low (1.3 mg/kg/day), suggesting calcium deficiency. However, retention of calcium (127 mg/kg/day) and phosphorus (76 mg/kg/day) was occurring at intrauterine rates. Thus, while calcium absorption was adequate at 10 weeks of age, the same was not true earlier in life. We suggest that there is a limiting role of calcium absorption on bone mineralization during early life in the VLBWI.