X-连锁低磷性佝偻病的基因突变分析

目的：研究X-连锁低磷性佝偻病（XLH）患儿致病基因的突变频率和突变类型,探讨存在突变热点的可能性及基因型与临床表型的关系。方法：回顾性分析10例XLH患儿的临床资料,评估其基因突变类型及其与疾病严重程度之间的关系。结果：10例XLH患儿均检测到PHEX基因突变,其中6例为错义突变,2例为拼接位点突变,1例为框移突变,1例为无义突变。还发现了两个新突变,即c.2048T>C 和IVS14+1delAG。PHEX基因的突变类型与矮小程度、腿弯程度之间没有关联（分别P=0.571、0.467）;基因的突变位置与矮小程度、腿弯程度之间也没有关联（分别P=0.400、1.000）。结论：错义突变是XLH患儿最常见的突变类型;c.2048T>C 和IVS14+1delAG是PHEX基因的两个新突变。PHEX基因的突变类型和突变位置与疾病的严重程度无相关性。     

X-连锁低磷性佝偻病的诊治进展

X-连锁低磷性佝偻病是最常见的遗传性佝偻病,临床亦不少见且容易误诊、漏诊,治疗与一般佝偻病相比更复杂.该文就X-连锁低磷性佝偻病的临床特征、致病基因以及治疗情况进行综述.     

3例低血磷性抗维生素D佝偻病的基因诊断及文献复习

对3例临床疑似X连锁低血磷抗维生素D佝偻病（XLH）患儿进行磷酸盐调节基因（PHEX）分析并确诊的临床资料进行回顾性分析及相关文献复习,探讨中国人存在的突变热点和突变类型。3例患儿均检测到PHEX基因突变,1例为无义突变（c.58C>T）,2例为剪接突变（c.1645+1G>A,c.436+1G>A）,其中c.436+1G>A为新突变。至2014年1月,世界上已报道的PHEX基因突变共有329个,错义突变占数量最多（24%）,突变热点区域有3个。不同地区的病例总数和突变类型存在差异。中国人群中,89例XLH病人进行了PHEX基因检测,发现28种突变,其中在22外显子上发现的突变数量最多（18%）,突变类型最多的为错义突变（61%）。总之,在中国人群中,XLH病人PHEX基因最常见的突变位置为第22外显子,最常见的突变类型为错义突变;c.436+1G>A 为PHEX基因的新突变。     

6例低血磷性抗D佝偻病误诊分析

在几种抗Ｄ佝偻病中 ,低血磷性抗Ｄ佝偻病较多见 ,其早期表现与最常见的维生素Ｄ缺乏性佝偻病十分相似 ,临床易造成长期误诊。近年来 ,我们在诊治儿童佝偻病时 ,误诊６例 ,现分析如下。临床资料本组男２例 ,女４例 ;年龄２．５～１０岁 ,平均３．５岁。病史最长５年 ,最短６个月 ,平均２．５年。其中来自农村４例 ,城郊２例。临床表现 :大多数以下肢行走无力 ,易摔跤 ,双下肢弯曲畸形 ,甚至出现“Ｘ”或“Ｏ”形腿且进行性加重 ,经一般维生素Ｄ治疗无效而就诊。６例中２例患儿母亲身材矮小 ,也有轻度双下肢“Ｏ”形腿畸形。其他体征如肋外翻…     

低血磷性佝偻病20例患儿诊断与治疗分析北大核心CSCD

目的分析20例低血磷性佝偻病（HR）患儿临床诊断及治疗资料,以提高临床对HR的诊断和治疗水平。方法回顾性分析2010年5月至2016年4月南京医科大学附属儿童医院收治的20例HR患儿的临床资料,总结其临床特点。20例HR患儿均行X染色体上与内肽酶同源的磷调节基因（PHEX）直接测序,未发现PHEX基因突变的患儿进一步采用多重连接探针扩增技术进行基因分析。结果20例HR患儿均有不同程度的生长迟缓、双下肢弯曲及典型的X线佝偻病表现。经治疗后临床表现好转,身高标准差数值（HSDS）随治疗时间的延长而明显改善,差异有统计学意义（P=0．027）。患儿血磷波动与继发性甲状旁腺功能亢进之间呈正相关（P〈0．05）。19例患儿检测到PHEX基因突变,以截断型突变为主,其中4种PHEX基因突变为首次报道。结论临床表现、实验室及影像学检查是HR诊断的临床指标,PHEX基因检测可作为本病诊断的重要辅助标准,早期诊断、及时治疗可明显改善患儿临床表现。     

重组人类生长激素治疗儿童X-连锁低血磷性佝偻病

目的评价重组人类生长激素(rhGH)治疗儿童X-连锁低血磷性佝偻病(XLH)的临床疗效与安全性。方法检查Cochrane囊性纤维化及遗传性疾病工作组建立的先天性代谢缺陷数据库。手检相关骨和矿物质代谢的杂志和会议摘要。纳入所有单独采用重组人类生长激素或联合传统疗法与安慰剂或单用传统疗法治疗儿童XLH作比较的随机对照试验或半随机对照试验。2个评价员独立选择纳入的试验、评价试验的方法学质量及提取数据。结果只有1个研究符合该系统评价的纳入标准，且样本鼍小。rhGH治疗可能改善XLH患儿身高增长，并可因暂时减少尿磷的排出而提高血磷水平。结论尚没有足够的证据显示rhGH是否对患儿的身高增长、矿物质代谢、内分泌、肾功能、骨矿密度和上下部量比例有影响。     

家族性低磷性抗维生素D佝偻病4个家系PHEX、FGF-23、DMP-1基因突变分析北大核心CSCD

目的分析来源于中国的4个家系6例家族性低磷性抗维生素D佝偻病(FHVDRR)患者的PHEX、FGF-23和DMP-1基因突变情况。方法采集4个FHVDRR家系成员及10例健康对照者的外周血血样,提取基因组DNA,聚合酶链反应(PCR)扩增,采用DNA直接测序法及TA克隆进行PHEX、FGF-23、DMP-1基因的外显子及侧翼序列测序,分析其基本突变。结果家系1中先证者及先证者姐姐在DMP-1基因第6外显子处发现DMP-1基因纯合同义突变(c1218 C>T,c1230 G>A),先证者母亲发现DMP-1基因杂合同义突变(c1218 C>T,c1230 G>A)。家系2中先证者在PHEX基因第12外显子处发现PHEX基因突变(c1333-1334GC>TT,p.A445F),TA克隆确认其为杂合突变,其父母及健康对照未发现相同突变;先证者及其母亲在FGF-23基因第3外显子处发现杂合突变(c716 C>T,p.T239M)。家系3中先证者在DMP-1基因第6外显子处发现DMP-1基因纯合突变(e205 A>T,p.S69C);同时发现在先证者和其父的FGF-23基因第3外显子处c716C>T,p.T239M突变。家系1、3、4中先证者及其他受累者未发现PHEX、FGF-23、DMP-1基因致病突变。结论PHEX基因c1333-1334 GC>TT,p.A445F突变可能是家系2中先证者患病病因,需进一步实验验证。家系2和家系3中发现的FGF-23基因c716 C>T,p.T239M突变,尚不确定其为发病原因,认为其不引起表型异常。     

低磷性佝偻病的新认识

低磷性佝偻病是儿童常见的代谢性骨病,是由于磷代谢失衡(先天遗传/后天获得)导致骨矿化障碍所造成的.磷的动态平衡依赖于一个复杂的骨-肾轴,其机制迄今知之甚少.现通过参与血磷代谢平衡的器官、细胞、激素、调节因子等进一步阐述低磷性佝偻病的发病机制,重点阐述成纤维细胞生长因子23、细胞外基质磷酸化糖蛋白、分泌型卷曲相关蛋白、成纤维细胞生长因子7等磷调节因子在低磷性佝偻病发病机制中的作用,以及常见低磷性佝偻病的诊断及治疗进展.     

2例X-连锁低血磷性佝偻病患者PHEX基因新发突变的研究

目的研究2例X-连锁低血磷性佝偻病(XLH)患儿及家系磷酸盐调节基因(PHEX)的突变类型,以明确其遗传学病因。方法回顾性分析2例XLH患者临床资料,应用高通量测序技术从基因组水平对先证者的XLH致病基因PHEX进行检测,并应用PCR-Sanger测序法对突变基因的家系分布进行验证。结果 2例患儿均检测到PHEX基因新发突变,1例为移码突变c.931dupC,导致翻译提前终止,产生截短蛋白p.Gln311Profs*13;另1例为剪接位点突变IVS14+1GA,导致外显子15跳跃,产生不完整的氨基酸链。2例患儿父母的基因表型均正常。结论 c.931dup C和IVS14+1GA是PHEX基因的两个新突变,可能是XLH新的致病性突变。     

X连锁显性遗传性低磷血症性佝偻病诊治专家共识

X连锁显性遗传性低磷血症性佝偻病(OMIM307800)为罕见的遗传病,是低磷血症性佝偻病最常见的类型,患病率约为1/20 000^ [1],1937年由Albright等^ [2]首次报道。患者多在开始走路、骨骼逐渐负重后才被发现,如果不能及早、正确治疗,将导致骨骼残疾及生长障碍,严重损害患者及其家庭的生存质量,如果及早诊治,预后良好。     

Growth in X-linked hypophosphatemic rickets

Growth failure appears frequently in children with X-linked hypophosphatemic rickets (XLHR) due to hypophosphatemia, disease severity, body disproportion, and primary bone abnormality. Recombinant human growth hormone (rhGH) increases phosphate tubular reabsorption and phosphate level in blood and, thus, constitutes an attractive but controversial therapy in short children with XLHR, those efficacy was demonstrated in small uncontrolled series. Our aim was to report our experience regarding growth in XLHR. Twenty-seven children with XLHR—20 girls, seven boys—diagnosed at a median (md) of 1.46 years of age, (range 0.39–8.5 years), were studied at 10.12 years of age (1.58–18.56), md (range). All received oral treatment with phosphate and calcitriol. At the first visit, grouped Z-height was −1; (−4.58; 0.54) md (range). After 5 years’ follow-up (0.92–15.6), Z-height was −0.91 (− 4.56; 0.17), not different from that at baseline (P = 0.465). In 16 children entirely controlled in our program upon presentation, a “catch up” phenomenon after the rickets had healed (P = 0.823) or throughout the long-term was not observed (P = 0.995). Eight patients had a Z-height ≤ −2SD at the last visit, and impaired linear growth was associated with age >2 years at diagnosis, male gender and non-adherence to treatment. Four children, all boys, received rhGH, and in two cases with sufficient follow up stature normalized. No rhGH side effects were observed, and phosphate and calcitriol doses remained stable. Linear growth failure appeared in a third of XLHR children. Efforts need to be made to reduce the age of diagnosis and to improve adherence to treatment. Treatment with rhGH should be considered early, after the rickets has been controlled, in those patients with impaired growth or delayed diagnosis.     

Early diagnosis and early treatment of hypophosphatemic vitamin D-resistant rickets

This is a report on two children with hypophosphatemic vitamin D-resistant rickets born to affected mothers diagnosed at the age of one and three months, respectively. The most important diagnostic criterium is the reduced value of the transport maximum of phosphorus in relation to glomerular filtration rate. At the age of one and six months, respectively, therapy with 1.25 (OH)2D3 and phosphate was started with the result of normal growth of length, radiological healing of rickets and normalisation of alkaline serum-phosphatase, but persistently low fasting values of serum-phosphorus during the time of observation up to twelve and twenty-four months of age, respectively in both children. The therapy with 1.25 (OH)2D3 and phosphate has a positive effect on intestinal absorption of phosphorus, because the serum-phosphorus is significantly elevated to the age corrected normal range two hours after oral administration of phosphate. There were no negative effects during therapy. It seems, therefore, that early diagnosis and therapy with 1.25 (OH)2D3 and phosphate is successful in healing this rare form of rickets.     

A clinical and molecular genetic study of hypophosphatemic rickets in children

X-linked hypophosphatemic rickets (XLH), autosomal dominant hypophosphatemic rickets, hereditary hypophosphatemic rickets with hypercalciuria, and tumor-induced osteomalacia share clinical and biochemical features, and are collectively referred to as hypophosphatemic rickets (HR). Recently, the molecular bases of HR were elucidated. A review of medical records and mutational analyses of the PHEX and FGF23 genes were performed on 17 unrelated Korean children with HR. The male-to-female ratio was 3:14, and 5 patients were familial. Initial laboratory tests revealed typical features of HR. Seven different PHEX mutations were detected in 8 patients: 2 missense mutations, 2 nonsense mutations, and 3 short deletions. No functional FGF23 mutation was detected in any patient. Patients with the PHEX mutation tended to have more severe skeletal disease than those without. Of the patients with this mutation, no genotype-phenotype correlation and no gene dosage effect were noted. Treatment with vitamin D and phosphate resulted in only a partial growth improvement in most cases, and was frequently complicated by hypercalciuria, hypercalcemia, nephrocalcinosis, or hyperparathyroidism. Renal glycosuria was detected in six cases and was associated with more severe skeletal disease. We conclude that current HR treatment is not fully safe or effective, and that close monitoring of treatment effectiveness and for complications should be performed during long-term treatment. No genotype-phenotype correlation in XLH was detected in this study, but a large-scaled study on this topic is warranted. The large proportion of patients with a normal genetic study suggests the possibility of other causative gene(s).     

一种新的磷调节因子:成纤维细胞生长因子23

血磷浓度的稳定对机体正常物质代谢具有重要意义.成纤维细胞生长因子23(fibroblast growth factor 23,FGF23)是人类新认识的调节血磷代谢的一种激素,其在慢性肾脏病(chronic kidney disease,CKD)、低血磷佝偻病和骨软化症中升高.FGF23由骨细胞产生,通过远距离调节肾脏对磷的排泄而维持血磷的内稳态,其发现无疑使人们对体内矿物质调节机制有了新的认识.     

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??Hypophosphatemic Vitamin D resistant rickets is a group of metabolic bone diseases characterized by increase renal excretion of phosphate and hypophosphatemia. Regulation of phosphate homeostasis includes a complicated feedback network??in which parathyroid hormone??PTH????fibroblast growth factor-23??FGF23?? and 1??25-??OH??D3 are key regulatory factors. With the understanding of phosphate regulation and the pathogenesis of this disease??progresses have been made in the diagnosis and treatment in hypophosphatemic rickets recently. In this review??based on the mechanisms of phosphate regulation??we explain the pathogenesis and clinical manifestations of hypophosphatemic rickets??and summarize up-to-date diagnostic and therapeutic approaches.     

Hemoglobin-oxygen affinity in hypophosphatemic rickets.

In 14 patients with simple X-linked hypophosphatemic rickets, 5 were below the third percentile in height and 9 were between the third and twenty-fifth percentile. Although the mean serum inorganic phosphorus level was only 2.01 +/- 0.65 (normal range for all age groups is 3.8 to 6.0 mg/100 ml), both the mean values for red cell 2,3-diphosphoglycerate (2,3-DPG) and adenosine triphosphate (ATP) were normal at 4.78 +/- 1.23 and 1.02 +/- 0.17 mumol/ml of red blood cells respectively. Moreover, the mean P50 value was normal at 26.4 +/- 0.9 mmHg. These normal oxygen transport data make unlikely any proposal that short stature seen in these patients is secondary to chronic tissue hypoxia. They also indicate that the intra-erythrocytic organic phosphate levels are maintained at normal levels despite profound chronic hypophosphatemia.     

Molecular aspects of familial hypophosphatemic rickets

Familial hypophosphataemic rickets (XLH) is an X-linked dominant disorder resulting in hypophosphataemia, abnormal regulation of 25-hydroxy vitamin D metabolism, elevated activity of alkaline phosphatase, bone deformities and short stature. In 1995-97 the sequence of PEX gene responsible for the disease was established. The PEX gene spreads 24.3 kb and includes 22 small exons coding a protein belonging to a neutral endopeptidase family. Function of the protein is not known yet. Mutation analysis in patients from North America, Africa and Europe (including Poland) revealed the presence of many different types of the PEX gene mutations. Identified deletions, insertions and substitution are supposed to change the structure of the PEX protein. Active form of vitamin D3, 1-alpha-hydroxylase and phosphate supplementation are now the recommended treatment of XLH patients. Further research is necessary to understand the role of the PEX protein in the pathogenesis of hypophosphatamic rickets.     

Fibrous dysplasia, phosphate wasting and fibroblast growth factor 23

Fibrous dysplasia (FD) is a classic feature of McCune-Albright syndrome (MAS). Renal phosphate wasting commonly occurs in FD, contributing to the mineralization defect in FD lesions and in non-FD bones, potentially increasing bone deformity. The presence of phosphate wasting correlates with measures of FD disease activity. Hypophosphatemia and phosphate wasting in FD are accompanied by inappropriately normal or low 1,25-dihydroxyvitamin D3 concentrations, similar to X-linked hypophosphatemic rickets. Recently, fibroblast growth factor 23 (FGF23) has emerged as an important humoral factor regulating phosphate and vitamin D homeostasis. FGF23 inhibits renal tubular phosphate reabsorption and decreases 1,25-dihydroxyvitamin D3. Interestingly, FGF23 is produced by normal osteoblasts as well as the abnormal osteogenic precursors present in FD lesions. However, FD lesions likely produce FGF23 in an unregulated fashion. Elevated circulating FGF23 correlates with total body FD disease burden and the presence of phosphate wasting. MAS mutations increase immature osteoblast lineage cells causing FD, resulting in dysregulated FGF23 production and, hence, phosphate wasting.