Bone Microarchitecture Assessment by HR-pQCT in Pediatric XLH Patients in China
Overview
This study evaluated bone geometry, density, microarchitecture, and stiffness using HR-pQCT in 106 Chinese pediatric and adolescent patients with X-linked hypophosphatemia (XLH). Compared to matched controls, XLH patients exhibited deteriorated bone microarchitecture, particularly in cortical bone, with correlations between disease activity marker ALP-Z and skeletal quality parameters.
Background
X-linked hypophosphatemia (XLH) is a heritable disorder characterized by renal phosphate wasting leading to hypophosphatemia, leg deformities, and short stature. Elevated FGF23 levels in XLH reduce phosphate reabsorption and vitamin D activation, impairing bone mineralization. Current clinical assessments rely on biochemical markers and radiographic scores, which do not directly quantify skeletal microarchitecture. High-resolution peripheral quantitative computed tomography (HR-pQCT) offers detailed evaluation of bone quality but is limited in availability, especially for pediatric populations.
Data Highlights
Parameter
XLH Patients
Controls
Significance
Trabecular Area (Tb.Ar)
Significantly higher
Lower
p < 0.05
Total Volumetric BMD
Lower
Higher
p < 0.05
Cortical Volumetric BMD (Ct.vBMD)
Lower
Higher
p < 0.05
Stiffness (Distal Radius and Tibia)
Lower
Higher
p < 0.05
ALP-Z Correlations
Negative with Ct.vBMD and cortical thickness; Positive with cortical porosity
Not applicable
Significant correlations
Key Findings
XLH pediatric and adolescent patients show significantly increased trabecular area and decreased volumetric bone mineral density compared to controls.
Cortical bone parameters, including cortical volumetric BMD and thickness, are reduced in XLH patients, indicating cortical deterioration.
Bone stiffness at distal radius and tibia is significantly lower in XLH patients, reflecting compromised bone strength.
Alkaline phosphatase Z score (ALP-Z), a marker of rickets activity, negatively correlates with cortical BMD and thickness and positively correlates with cortical porosity.
An online calculator was developed to estimate HR-pQCT parameters from clinical and biochemical data, facilitating skeletal assessment where HR-pQCT is unavailable.
Clinical Implications
HR-pQCT reveals significant cortical and trabecular bone deterioration in pediatric XLH patients, underscoring the importance of monitoring bone quality beyond standard biochemical markers. The correlation of ALP-Z with cortical bone parameters suggests its utility in tracking disease activity and skeletal health. The developed estimation tool can aid clinicians in assessing bone microarchitecture in settings lacking HR-pQCT access, potentially improving management and treatment decisions.
Conclusion
Adolescent and pediatric patients with XLH exhibit marked deterioration in bone microarchitecture and stiffness, particularly in cortical bone, as assessed by HR-pQCT. Clinical and biochemical indicators, including ALP-Z, can help estimate skeletal quality, supporting improved disease monitoring and management.
References
Assessment of Bone Microarchitecture Using HR-PQCT in Pediatric and Adolescent Patients with X-Linked Hypophosphatemia in China
