Bone microarchitecture evaluated by HR-pQCT in Chinese adolescent and pediatric patients with X-linked hypophosphatemia

Context: X-linked hypophosphatemia (XLH) is the most common form of heritable hypophosphatemic rickets. Previous studies have found deteriorated bone microarchitecture in the XLH adults. Detailed studies on the skeletal microarchitecture of XLH adolescent and pediatric patients are still lacking.

Objective: This study aimed to evaluate bone geometry, density, microarchitecture, stiffness in XLH adolescent and pediatric patients by using high-resolution peripheral quantitative computed tomography (HR-pQCT).Method: This study utilized HR-pQCT to assess bone geometry, density, microarchitecture, and stiffness in 106 Chinese adolescent and pediatric patients with XLH.

Result: Compared with the sex- and age-matched controls, XLH patients had significantly higher trabecular area (Tb.Ar), lower total volumetric bone mineral density (Tot.vBMD), lower cortical volumetric BMD (Ct.vBMD), and lower stiffness at both the distal radius and the tibia after adjusting for height and weight. Alkaline phosphatase Z score (ALP-Z), a marker to reflect the disease activity of rickets, was negatively correlated with Ct.vBMD and cortical thickness (Ct.Th) at the distal radius, and Ct.vBMD at the distal tibia, and positively correlated with cortical porosity (Ct.Po) at the distal tibia. We developed an online calculator to estimate Tb.Ar, Ct.vBMD, and stiffness of the distal tibia of XLH adolescent and pediatric patients based on clinical general characteristic and biochemical indicators.

Conclusion: The bone microarchitecture of XLH adolescent and pediatric patients was deteriorated, and ALP-Z was negatively correlated with the skeletal quality of XLH adolescent and pediatric patients, especially in the cortical bone. HR-pQCT parameters can be estimated using clinical characteristics and biochemical indicators, which may assist physicians to monitor the disease progression in areas without HR-pQCT access.