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Hypercalciuria in osteogenesis imperfecta: a follow-up study to assess renal effects
A Chines1, A Boniface, W McAlister
1Metabolic Research Unit, Shriners Hospital for Crippled Children, St. Louis, MO 63131, USA.
Insights
Pediatric osteogenesis imperfecta (OI) patients with hypercalciuria show persistent high urine calcium levels despite dietary changes. Kidney function remains normal in these children, but long-term effects require further study.
Area of Science:
- Pediatric Nephrology
- Skeletal Dysplasias
- Metabolic Bone Disease
Background:
- Hypercalciuria is a common finding in pediatric patients with osteogenesis imperfecta (OI).
- Previous studies reported 36% of OI patients exhibited hypercalciuria.
Purpose of the Study:
- To prospectively evaluate renal function in pediatric OI patients with a history of hypercalciuria.
- To assess the persistence of hypercalciuria and potential adverse effects on kidney health over time.
Main Methods:
- Prospective screening of 12 hypercalciuric pediatric OI patients.
- Assessment of dietary calcium intake, urine calcium/creatinine ratio, and kidney function tests (urinalysis, urine osmolality, creatinine clearance).
- Renal ultrasonography to screen for nephrocalcinosis or nephrolithiasis.
Main Results:
- 8 out of 12 patients remained hypercalciuric despite a 30% decrease in dietary calcium intake.
- Urinary calcium levels significantly correlated with skeletal disease severity (r = -0.75, p = 0.005).
- All patients exhibited normal routine urinalysis, concentrating ability, creatinine clearance, and renal ultrasonography findings.
Conclusions:
- Hypercalciuria persists in a majority of pediatric OI patients despite reduced calcium intake.
- No significant renal compromise was detected in this cohort of hypercalciuric pediatric OI patients.
- Long-term renal effects in adult OI patients, particularly those severely affected, warrant further investigation.
Abstract:
In 1991, we reported that hypercalciuria is a common finding in our pediatric patient population with osteogenesis imperfecta (OI) (17 of 47 = 36%). Here, we prospectively screened 12 of these hypercalciuric children, on average 4 years subsequent to the discovery of elevated urine calcium levels, for adverse effects on renal function. Despite an ad libitum decrease since initial investigation of about 30% in their previously normal dietary calcium intake (adjusted for body weight), 8 of the 12 patients remained hypercalciuric (urine calcium/creatinine > 0.62 mmol/mmol). We found, once again, that urinary calcium levels significantly correlated with the severity of the skeletal disease as assessed by z-score for height (r = -0.75, p = 0.005). Evaluation of kidney function, however, revealed: (i) normal routine urinalysis in all but 1 subject who had transient microscopic hematuria; (ii) unremarkable concentrating ability determined by fasting urine osmolality; (iii) normal creatinine clearance, and (iv) unremarkable ultrasonography to measure renal size and to screen for nephrocalcinosis or nephrolithiasis. Although no significant renal compromise was detected with these studies in our hypercalciuric pediatric OI patients, investigation of affected adults, especially those severely affected, will be important to assess whether this is a long-term problem and if adverse effects on the kidneys do develop.