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Hypercalciuria in children severely affected with osteogenesis imperfecta
A Chines1, D J Petersen, F W Schranck
1Metabolic Research Unit, Shriners Hospital for Crippled Children, St. Louis, MO 63131.
Insights
Hypercalciuria, or high urinary calcium, is common in children with osteogenesis imperfecta. Its severity correlates with the skeletal disorder
Area of Science:
- Pediatric Nephrology
- Pediatric Endocrinology
- Skeletal Dysplasias
Background:
- Osteogenesis imperfecta (OI) is a genetic disorder characterized by brittle bones.
- Hypercalciuria is a condition of elevated calcium levels in the urine.
- The prevalence and significance of hypercalciuria in pediatric OI patients are not well-established.
Purpose of the Study:
- To determine the frequency of hypercalciuria in children with osteogenesis imperfecta.
- To investigate the relationship between hypercalciuria and disease severity in pediatric OI.
Main Methods:
- Retrospective analysis of pediatric patients with osteogenesis imperfecta.
- Evaluation of mineral homeostasis, including urinary calcium levels.
- Assessment of bone mineral density and histomorphometric bone parameters.
Main Results:
- Hypercalciuria was identified in 36% of pediatric OI patients.
- Hypercalciuric children were shorter and had a higher lifelong fracture rate.
- Urinary calcium levels negatively correlated with height z-scores in hypercalciuric patients.
Conclusions:
- Hypercalciuria is a frequent finding in children with osteogenesis imperfecta.
- The degree of hypercalciuria appears to be associated with the severity of osteogenesis imperfecta.
- Further research is warranted to explore the clinical implications of hypercalciuria in pediatric OI.
Abstract:
To investigate our impression that hypercalciuria is relatively common in children with osteogenesis imperfecta, we performed a retrospective study of data accumulated from our pediatric population with this skeletal disorder. Children with osteogenesis imperfecta (17 girls, 30 boys; mean (+/- SD) age 7.8 +/- 4.6 years; range 0.7 to 16.8 years) had undergone detailed inpatient evaluation of mineral homeostasis during periods of clinical stability and controlled dietary calcium intake. Hypercalciuria was found in 36% of the patients and averaged (+/- SEM) 6.1 +/- 0.3 mg/kg per 24 hours (0.15 +/- 0.01 mmol/kg per 24 hours) or 392 +/- 28 mg/gm of creatinine (1.10 +/- 0.07 mmol calcium/mmol creatinine) in the group with hypercalciuria. There were no statistically significant differences in age, gender, or dietary calcium intake (per kilogram of body weight) between the normocalciuric and hypercalciuric children. However, the group with hypercalciuria was shorter than the normocalciuric group and had a greater lifelong fracture rate. When patient height z scores were regressed against urinary calcium levels, a significant negative correlation was found in the group with hypercalciuria (r = -0.76; p less than 0.001). Although serum alkaline phosphatase activity was lower in the group with hypercalciuria, no difference was found between groups with regard to serum levels of calcium, phosphate, magnesium, creatinine, immunoreactive parathyroid hormone, or osteocalcin. The groups were also similar with respect to both their total body mineral density, as determined by dual-photon absorptiometry (n = 17), and their static indexes of bone formation and resorption, as assessed histomorphometrically with iliac crest specimens (n = 19). We conclude that hypercalciuria occurs frequently in children with osteogenesis imperfecta, and that its magnitude appears to reflect the severity of the skeletal disease.