Effect of burosumab conversion on calciuria and nephrocalcinosis in children with XLH: A real-world cohort study.
retrospective_cohort · Level III
Where this comes from
- Record sourced from PubMed, PMID 41035763.
- Also identified by DOI 10.1016/j.bonr.2025.101877 and PMC identifier 12481703.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Burosumab, a monoclonal antibody to fibroblast growth factor 23 (FGF23), is effective for X-linked hypophosphatemic rickets (XLH). Renal effects, particularly calciuria and nephrocalcinosis, remain incompletely characterized. In this retrospective cohort, 13 children with genetically confirmed XLH (7 females, 6 males; 0.6-16.3 years) were evaluated after conversion from conventional therapy to burosumab. Longitudinal changes in serum phosphate, TmP/GFR, TRP, 1,25(OH)₂D, intact parathyroid hormone (PTH), and urinary calcium/creatinine (Ca:Cr) were assessed. Hypercalciuria was defined using age-specific SI thresholds; Ca:Cr was also expressed as ×ULN (Ca:Cr divided by the age-specific upper limit). Burosumab improved serum phosphate (<i>p</i> < 0.001), TmP/GFR (p < 0.001), and TRP (<i>p</i> = 0.007). Despite normalized phosphate handling, two patients developed de novo nephrocalcinosis. No child was hypercalciuric at washout or Day 14; two had ≥1 episode later. A repeated-measures analysis of log10(×ULN) showed no overall time effect from washout to Day 56 (F(4,29) = 1.66, <i>p</i> = 0.185). A larger decline in PTH correlated with higher Ca:Cr (<i>p</i> < 0.05), whereas 1,25(OH)₂D did not. Burosumab improves phosphate homeostasis in children with XLH, but a minority may develop hypercalciuria and nephrocalcinosis, potentially linked to PTH suppression. Vigilant biochemical and ultrasound monitoring-particularly early after conversion-and consideration of prophylaxis in high-risk cases are advisable.