PURPOSE To examine the MRI diagnostic performance in the assessment of therapeutic response to burosumab in children with X-linked hypophosphatemia (XLH). DESIGN Prospective longitudinal open cohort. PATIENTS Seventeen children with XLH, average age of 10.2 ± 2.7 years, had a knee MRI at baseline and after 1 year of burosumab. INTERVENTION Children received burosumab at an average dose of 1.4 ± 0.5 mg/kg during 1 year for the treatment of severe rickets (the target serum phosphate ≥ 1.2 mmol/L (≥3.7 mg/dL). The primary endpoint was the change from baseline to 12 months in rachitic lesions on knee MRI. Secondary endpoints were changes in biochemical parameters of phosphate and alkaline phosphatase (ALP). RESULTS One year of treatment with burosumab significantly reduced radiological disease activity on knee MRI (by 44 ± 29% in the transverse extent of widening) which was accompanied by a significant reduction in biochemical activity, namely in serum ALP activity, by 28 ± 17%. Additionally, MRI parameters after 1 year of treatment with burosumab (the maximum width of medial physis at 12 months and the change from baseline in the maximum width of lateral physis) were associated with ALP activity at 12 months. CONCLUSION We suggest that MRI is a valuable and quantitative tool to evaluate the therapeutic response to burosumab. MRI could be an excellent alternative to standard bone radiographs for evaluation of the rachitic lesions in a clinical setting avoiding repeated exposition to ionizing radiation.

中文翻译：

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磁共振成像是评估 burosumab 治疗 X 连锁低磷血症儿童疗效的重要工具。

目的 检查 MRI 诊断性能在评估 X 连锁低磷血症 (XLH) 儿童对布罗单抗的治疗反应中的作用。设计前瞻性纵向开放队列。患者 17 名 XLH 儿童，平均年龄为 10.2 ± 2.7 岁，在基线和 burosumab 治疗 1 年后接受了膝关节 MRI 检查。干预 儿童在 1 年内接受 burosumab 的平均剂量为 1.4 ± 0.5 mg/kg 治疗严重佝偻病（目标血清磷酸盐≥ 1.2 mmol/L (≥3.7 mg/dL)。主要终点是与基线的变化膝关节 MRI 显示佝偻病病变 12 个月。次要终点是磷酸盐和碱性磷酸酶 (ALP) 生化参数的变化。结果 用 burosumab 治疗一年后，膝关节 MRI 的放射疾病活动显着降低（横向扩展范围降低 44 ± 29%），同时生化活性显着降低，即血清 ALP 活性降低 28 ± 17% . 此外，burosumab 治疗 1 年后的 MRI 参数（12 个月时内侧骺的最大宽度和外侧骺最大宽度相对于基线的变化）与 12 个月时的 ALP 活性相关。结论 我们建议 MRI 是一种有价值的定量工具来评估对布罗单抗的治疗反应。MRI 可以作为标准骨 X 光片的绝佳替代品，用于评估临床环境中的佝偻病病变，避免反复暴露于电离辐射。