Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini 6, 50139 Florence, Italy.
F.I.R.M.O. Italian Foundation for the Research on Bone Diseases, Via San Gallo 123, 50129 Florence, Italy.
Genes (Basel). 2022 Dec 19;13(12):2415. doi: 10.3390/genes13122415.
X-linked hypophosphatemia (XLH) is the most common hereditary form of rickets and deficiency of renal tubular phosphate transport in humans. XLH is caused by the inactivation of mutations within the phosphate-regulating endopeptidase homolog X-linked () gene and follows an X-dominant transmission. It has an estimated frequency of 1 case per 20,000, and over 300 distinct pathogenic variations have been reported that result in an excess of fibroblast growth factor 23 (FGF23) in the serum. Increased levels of FGF23 lead to renal phosphate loss, decreased serum 1,25-dihydroxyvitamin D, and increased metabolism of 1,25-dihydoxyvitamin D, resulting in hypophosphatemia. Major clinical manifestations include rickets, bone deformities, and growth retardation that develop during childhood, and osteomalacia-related fractures or pseudo-fractures, degenerative osteoarthritis, enthesopathy, dental anomalies, and hearing loss during adulthood, which can affect quality of life. In addition, fatigue is also a common symptom in patients with XLH, who experience decreased motion, muscle weakness, and pain, contributing to altered quality of life. The clinical and biomedical characteristics of XLH are extensively defined in bone tissue since skeletal deformations and mineralization defects are the most evident effects of high FGF23 and low serum phosphate levels. However, despite the muscular symptoms that XLH causes, very few reports are available on the effects of FGF23 and phosphate in muscle tissue. Given the close relationship between bones and skeletal muscles, studying the effects of FGF23 and phosphate on muscle could provide additional opportunities to understand the interactions between these two important compartments of the body. By describing the current literature on XLH and skeletal muscle dysfunctions, the purpose of this review is to highlight future areas of research that could contribute to a better understanding of XLH muscular disability and its management.
X 连锁低磷血症(XLH)是人类最常见的遗传性佝偻病和肾小管磷酸盐转运缺陷。XLH 是由磷酸盐调节内肽酶同源物 X 连锁()基因突变失活引起的,呈 X 显性遗传。其估计发病率为每 20,000 例 1 例,已报道超过 300 种不同的致病变异,导致血清中纤维母细胞生长因子 23(FGF23)过多。FGF23 水平升高导致肾脏磷酸盐丢失、血清 1,25-二羟维生素 D 减少和 1,25-二羟维生素 D 代谢增加,导致低磷血症。主要临床表现包括儿童期发生的佝偻病、骨骼畸形和生长迟缓,以及成年期相关的骨软化症骨折或假性骨折、退行性骨关节炎、肌腱病、牙齿异常和听力丧失,这些都会影响生活质量。此外,疲劳也是 XLH 患者的常见症状,他们会出现运动减少、肌肉无力和疼痛,从而导致生活质量改变。XLH 的临床和生物医学特征在骨骼组织中得到广泛定义,因为骨骼畸形和矿物质化缺陷是高 FGF23 和低血清磷酸盐水平的最明显影响。然而,尽管 XLH 会导致肌肉症状,但关于 FGF23 和磷酸盐对肌肉组织的影响的报道非常少。鉴于骨骼和骨骼肌之间的密切关系,研究 FGF23 和磷酸盐对肌肉的影响可能为进一步了解这两个身体重要部位之间的相互作用提供机会。通过描述关于 XLH 和骨骼肌肉功能障碍的现有文献,本综述的目的是强调未来的研究领域,这可能有助于更好地理解 XLH 肌肉功能障碍及其管理。
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