Rickets in a very low birth weight infant

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.