Abstract：
An 18-month-old male presented with gross motor delay and poor growth (weight z-score -2.21, length z-score -4.26). Radiographs showed metaphyseal irregularities suggesting metaphyseal dysplasia and sagittal craniosynostosis. Biochemical evaluation supported hypophosphatemic rickets [serum phosphorus 2.3 mg/dL (reference range (RR) 4.3-6.8), alkaline phosphatase 754 unit/L (RR 156-369)] due to renal phosphate wasting (TmP/GFR 4.3 mg/dL, normal for age 4.3-6.8), with C-terminal fibroblast growth factor 23 (FGF23) 125 RU/mL (>90 during hypophosphatemia suggests FGF23-mediated hypophosphatemia). Treatment was initiated with calcitriol and phosphate. Genetic analysis showed a pathogenic variant of FGF23: c.527G > A (p.Arg176Gln) indicative of autosomal dominant hypophosphatemic rickets (ADHR). Consistent with reports linking iron deficiency with the ADHR phenotype, low ferritin was detected. Following normalization of ferritin level (41 ng/mL) with oral ferrous sulfate replacement, biochemical improvement was demonstrated (FGF23 69 RU/mL, phosphorus 5.0 mg/dL and alkaline phosphatase 228 unit/L). Calcitriol and phosphate were discontinued. Three years later, the patient demonstrated improved developmental milestones, linear growth (length Z-score -2.01), radiographic normalization of metaphyses, and stabilization of craniosynostosis. While the most common cause of hypophosphatemic rickets is X-linked hypophosphatemia, other etiologies should be considered as treatment differs. In ADHR, normalization of iron leads to biochemical and clinical improvement.
摘要：
一名18个月大的男性表现为运动严重延迟和生长不良（体重z评分-2.21，身长z评分-4.26）。X线照片显示干phy端不规则，提示干phy端发育不良和矢状颅骨融合。生化评估显示有低磷酸盐血症病的证据[血清磷2.3mg/dL（参考范围（RR）4.3-6.8），碱性磷酸酶754单位/L（RR156-369）]由于肾磷酸盐消耗（TmP/GFR4.3mg/dL，4.3-6.8岁正常)，C端FGF23125RU/mL（低磷酸盐血症期间>90提示FGF23介导的低磷酸盐血症）。用骨化三醇和磷酸盐开始治疗。遗传分析显示FGF23的致病变体：c.527G>A（p。Arg176Gln）指示常染色体显性低磷酸盐血症性病（ADHR）。与铁缺乏与ADHR表型相关的报道一致，检测到低铁蛋白，18ng/mL（RR24-336）。开始口服硫酸亚铁替代治疗。铁蛋白水平（41ng/mL）正常化后，证明了生化改善（FGF2369RU/mL，磷5.0mg/dL和碱性磷酸酶228单位/L)。停用骨化三醇和磷酸盐。三年后,患者表现出改善的发展里程碑，线性生长（长度Z分数-2.01），X线照相标准化，和颅骨融合的稳定。虽然低磷酸盐血症的最常见原因是X连锁低磷酸盐血症，其他病因应考虑为治疗不同。在ADHR中，铁的正常化导致生化和临床改善。
