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Congenital rickets. Study of the evolution of secondary hyperparathyroidism
Insights
This case study details nutritional rickets in a premature infant born to a mother with vitamin D deficiency. Findings suggest impaired conversion of 25-hydroxycholecalciferol to its active form, impacting bone health.
Area of Science:
- Pediatrics
- Endocrinology
- Nutritional Science
Background:
- Congenital rickets can occur due to nutritional deficiencies, particularly vitamin D.
- Premature infants are at higher risk for nutritional deficiencies and related complications.
Observation:
- A premature infant (34 weeks gestation, 1100g) presented with radiological signs of rickets at birth and 16 days.
- Biochemical analysis revealed hypocalcemia, hypophosphatemia, elevated alkaline phosphatase, and significantly high parathyroid hormone levels.
- Maternal plasma 25-hydroxycholecalciferol was low, indicating vitamin D deficiency during pregnancy.
Findings:
- Vitamin D2 administration showed partial healing but persistent biochemical abnormalities.
- Oral 25-hydroxycholecalciferol improved plasma levels but led to osteoporosis, suggesting reduced conversion to the active metabolite, 1,25-dihydroxycholecalciferol.
- Calcium infusion temporarily suppressed parathyroid hormone levels.
Implications:
- This case highlights a potential defect in vitamin D metabolism in premature infants born to deficient mothers.
- It underscores the importance of assessing vitamin D status in both mother and infant, especially in preterm neonates.
- Further investigation into the conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol is warranted in such cases.
Abstract:
A case of congenital rickets of nutritional origin is described in a light-for-date premature infant (gestational age 34 weeks, birthweight 1 100 g). X-rays of the long bones showed spread, frayed and cupped metaphyses at birth and at the age of 16 days. Serum calcium was 8.2 mg/100 ml, phosphorus 3.4 mg/100 ml and alkaline phosphatase (A.P):323 IU/ml (N less than or equal to 200) at the age of 3 days. Very high level of serum immunoreactive parathroid hormone (iPTH) was found at the age of 16 days=295 micronlEq/ml (N less than or equal to 50). Evidence of maternal vitamin D deficiency was demostrated by low plasma 25-hydroxycholecalciferol (25-OH-CC):1.0 ng/ml (N:13.2+/-4.2) soon after delivery; it was found to be normal (10.2 ng/ml) six months later. Ca infusion (15 mg/kg/3 h) resulted in a marked fall of serum iPTH (280 to 84 micronlEq/ml). Administration of vitamin D2 (2400 IU/day for 10 days) induced some healing of the metaphyses; A. P. remained elevated (400 IU/ml); plasma 25-OH-CC was normal 10.2 ng/ml and serum iPTH was 115 micronlEq/ml. When 25-OH-CC was given orally for ten days (15 microng/day), plasma 25-OH-CC rose to 64.5 ng/ml with a minor change of serum iPTH (94 micronlEq/ml); X-rays of the bones showed osteoporosis. These results suggest a reduced convertion of 25-OH-CC into 1-25-(OH)2-CC.