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Rickets in a very low birth weight infant
1Department of Pediatrics, University of Tennessee, Memphis.
Insights
This study reports a case of rickets in a very low birth weight infant (VLBWI) despite adequate vitamin D. Early life calcium absorption limitations may impede bone mineralization in VLBWIs.
Area of Science:
- Neonatal Nutrition
- Pediatric Bone Metabolism
- Nutritional Rickets
Background:
- Rickets is a significant concern in preterm infants.
- This case involves a very low birth weight infant (VLBWI) fed a specialized preterm formula with vitamin D supplementation.
- No typical high-risk factors for rickets were identified in this infant.
Observation:
- The infant received 200 IU of vitamin D daily by 10 days of age, with enteral feeds reaching 120 cal/kg/day by day 20.
- Mean nutrient intake between days 20-61 included calcium (185 mg/kg/day), phosphorus (93 mg/kg/day), and vitamin D (367 IU/day).
- Rickets was diagnosed on day 62, with a nutrient balance study revealing low urinary calcium excretion (1.3 mg/kg/day).
Findings:
- Despite low urinary calcium, calcium (127 mg/kg/day) and phosphorus (76 mg/kg/day) retention rates were comparable to intrauterine levels.
- Calcium absorption was adequate by 10 weeks of age.
- Adequate calcium absorption occurred later in infancy, not during the early critical period.
Implications:
- Early life calcium absorption may be a limiting factor for bone mineralization in very low birth weight infants.
- This highlights potential challenges in achieving optimal bone health in preterm neonates.
- Further research into optimizing calcium absorption strategies for VLBWIs is warranted.
Abstract:
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.