The clinical data of three Chinese children who had been definitely diagnosed with X-link dominate hypophosphatemic rickets (XLH) by gene mutation analysis of phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX) were retrospectively studied and the relevant literature was reviewed. PHEX gene mutations were detected in all 3 XLH children; a nonsense mutation (c.58C>T) in one case and splicing mutations (c.1645+1G>A, c.436+1G>A) in the other two cases. Among these mutations, c.436+1G>A was novel. As of January 2014, a total of 329 PHEX gene mutations were reported, primarily within three mutation hot spots, throughout the world. Missense mutations accounted for the highest proportion (24%) among all mutations. There is literature showing geographic differences in the total number of XLH subjects and PHEX mutation types across the world. In the current literature, 89 cases of XLH with 28 types of PHEX mutations have been reported in the population of mainland China. Exon 22 is the most frequent mutation site (18%) and missense mutations are the most common type of mutations (61%). It is concluded that exon 22 is the mutation hot spot and missense mutation is the most common type of mutation in the PHEX gene in Chinese XLH patients and that c.436+1G>A detected in this study is a novel PHEX gene mutation in Chinese with XLH.
Child ; Child, Preschool ; Familial Hypophosphatemic Rickets ; genetics ; Female ; Humans ; Male ; Mutation ; PHEX Phosphate Regulating Neutral Endopeptidase ; genetics

OBJECTIVE: To detect pathological variant in a Chinese pedigree affected with X-linked hypophosphatemia (XLH). METHODS: Whole-exome sequencing was carried out to screen genetic variants in the proband and her parents. Candidate variant of the phosphate regulating gene with homologies to endopeptidases on the X chromosome (PHEX) was verified by Sanger sequencing of all members of the pedigree and the 100 healthy controls. Prenatal diagnosis was carried out on chorionic villi sample derived from the fetus of the proband. RESULTS: A c.1256G>A (p. Gly419Glu) variant was identified in the PHEX gene of the proband and all other patients from this pedigree. The same variant was not found among healthy members from this pedigree and the 100 healthy controls. Prenatal diagnosis suggested that the fetus also carried the c.1256G>A (p. Gly419Glu) variant. CONCLUSION The c.1256G>A (p. Gly419Glu) variant of the PHEX gene probably underlay the pathogenesis of XLH in this family. Discovery of the novel variant has enriched the mutational spectrum of the PHEX gene.
China ; Familial Hypophosphatemic Rickets ; Female ; Humans ; Mutation ; PHEX Phosphate Regulating Neutral Endopeptidase/genetics* ; Pedigree ; Pregnancy ; Prenatal Diagnosis

X-linked hypophosphatemic rickets (XLH) results from mutations in the PHEX gene. Mutational analysis of the PHEX gene in 15 unrelated Korean patients with hypophosphatemic rickets revealed eight mutations, including five novel mutations, in nine patients: two nonsense mutations, two missense mutations, one insertion, and three splicing acceptor/donor site mutations. Of these, c.64G>T, c.1699C>T, c.466_467 insAC, c.1174-1G>A, and c.1768+5G>A were novel mutations. To analyze the correlation between genotype and phenotype, phenotypes were compared between groups with and without a mutation, in terms of mutation location, mutation type, and sex. Skeletal disease tended to be more severe in the group with a mutation in the C-terminal half of the PHEX gene, but no genotype-phenotype correlation was detected in other comparisons. Further extensive studies of the PHEX gene mutations and analyses of the genotype-phenotype relationships are required to understand PHEX function and the pathogenesis of XLH.
Adolescent ; Adult ; Child ; Child, Preschool ; Female ; Gene Dosage ; Genotype ; Humans ; Hypophosphatemic Rickets, X-Linked Dominant/*genetics ; Infant ; Male ; Middle Aged ; *Mutation ; PHEX Phosphate Regulating Neutral Endopeptidase/*genetics ; Phenotype

OBJECTIVETo explore the clinical characteristics and genetic mutation in a family affected with hypophosphatemic rickets.

METHODSWhole exome sequencing (WES) was used to screen potential mutations in genomic DNA extracted from peripheral venous blood sample from the proband. Suspected mutation was confirmed with Sanger sequencing. Amniotic fluid was sampled from the proband for prenatal diagnosis. Potential maternal contamination was excluded by analysis of short tandem repeat (STR) markers.

RESULTSWES has identified a heterozygous c.2058_2059insAGTT (p.L686fs) mutation of the PHEX gene in the proband, which was confirmed by Sanger sequencing in other affected individuals from the family. The mutation was detected in the amniotic fluid sample from the fetus but not among healthy members from the family.

CONCLUSIONIdentification of the PHEX mutation by WES has facilitated genetic counseling and prenatal diagnosis for the family affected with hypophosphatemic rickets.

Adult ; DNA Mutational Analysis ; Exome ; Familial Hypophosphatemic Rickets ; diagnosis ; genetics ; Female ; Humans ; Microsatellite Repeats ; Mutation ; PHEX Phosphate Regulating Neutral Endopeptidase ; genetics ; Pregnancy ; Prenatal Diagnosis ; Whole Genome Sequencing

OBJECTIVETo investigate the frequency and type of PHEX gene mutations in children with X-linked hypophosphatemic rickets (XLH), the possible presence of mutational hot spots, and the relationship between genotype and clinical phenotype.

METHODSClinical data of 10 children with XLH was retrospectively reviewed. The relationship between gene mutation type and severity of XLH was evaluated.

RESULTSPHEX gene mutations were detected in all 10 children with XLH, including 6 cases of missense mutation, 2 cases of splice site mutation, 1 case of frameshift mutation, and 1 case of nonsense mutation. Two new mutations, c.2048T>C and IVS14+1delAG, were found. The type of PHEX gene mutation was not associated with the degree of short stature and leg deformity (P=0.571 and 0.467), and the mutation site was also not associated with the degree of short stature and leg deformity (P=0.400 and 1.000).

CONCLUSIONSMissense mutation is the most common type of PHEX gene mutation in children with XLH, and c.2048T>C and IVS14+1delAG are two new PHEX gene mutations. The type and site of PHEX gene mutation are not associated with the severity of XLH.

Adolescent ; Child ; Child, Preschool ; Familial Hypophosphatemic Rickets ; genetics ; Female ; Humans ; Infant ; Male ; Mutation ; PHEX Phosphate Regulating Neutral Endopeptidase ; genetics ; Retrospective Studies

OBJECTIVETo screen potential mutations of PHEX gene in a family featuring hypophosphatemic rickets in order to confirm the molecular diagnosis and pathogenetic mechanism.

METHODSGenomic DNA was extracted from peripheral venous blood samples. DNA sequence of PHEX gene was derived from UCSC database, and primers for its coding region were designed with Primer premier 5.0. Potential mutations were detected with PCR amplification and DNA sequence analysis.

RESUTLSA mutation was identified in intron 6 of the PHEX gene in the proband and his mother.

CONCLUSIONThe c.732+1G>T mutation underlies the hypophosphatemic rickets in this family.

Adult ; Base Sequence ; Child ; Female ; Humans ; Hypophosphatasia ; enzymology ; genetics ; Introns ; Male ; Molecular Sequence Data ; Mutation ; PHEX Phosphate Regulating Neutral Endopeptidase ; genetics ; Pedigree

OBJECTIVETo investigate PHEX gene mutations in 2 patients with X-linked hypophosphatemic rickets (XLH) and their families and to clarify the genetic etiology.

METHODSA retrospective analysis was performed for the clinical data of two patients with XLH. High-throughput sequencing was used to detect the PHEX gene, a pathogenic gene of XLH. PCR-Sanger sequencing was used to verify the distribution of mutations in families.

RESULTSBoth patients had novel mutations in the PHEX gene; one patient had a frameshift mutation, c.931dupC, which caused early termination of translation and produced the truncated protein p.Gln311Profs*13; the other patient had a splice site mutation, IVS14+1G>A, which caused the skipping of exon 15 and produced an incomplete amino acid chain. Their parents had normal gene phenotypes.

CONCLUSIONSc.931dupC and IVS14+1G>A are two novel mutations of the PHEX gene and might be the new pathogenic mutations of XLH.

Child ; Child, Preschool ; Familial Hypophosphatemic Rickets ; genetics ; Female ; High-Throughput Nucleotide Sequencing ; Humans ; Male ; Mutation ; PHEX Phosphate Regulating Neutral Endopeptidase ; genetics ; Retrospective Studies

There are currently no published cases that report concomitant Turner syndrome (TS), 2q37 deletion syndrome and X-linked hypophosphatemic rickets (XLH). Interestingly, since the clinical phenotypes of TS and 2q37 deletion syndrome overlap, the correct diagnosis may be missed without a standardized approach to genetic testing consisting of both karyotype and microarray. Both chromosome anomalies have been associated with short stature and a variety of skeletal abnormalities however to date no reports have associated these syndromes in association with a phosphate regulating endopeptidase homolog, X-linked (PHEX) gene deletion resulting in XLH. We report a 3-year-old female with 3 concurrent genetic disorders including a 9.98 Mb terminal deletion of chromosome 2: del(2)(q37.1;q37.3), XLH secondary to a small microdeletion of part of the PHEX gene, and mosaic TS (mos 45,X[32]/46,X[18]). This is the first case report of a patient with 2q37 deletion syndrome and mosaic TS (mos 45,X[32]/46,X[18]) found to have XLH secondary to an interstitial constitutional PHEX gene deletion. Her severe phenotype and multiple genotypic findings reinforce the importance of thorough genetic testing in the setting of complicated phenotypic presentations.
Bone Diseases ; Child, Preschool* ; Chromosomes, Human, Pair 2 ; Diagnosis ; Familial Hypophosphatemic Rickets* ; Female* ; Gene Deletion ; Genetic Testing ; Humans ; Karyotype ; Microarray Analysis ; Phenotype ; PHEX Phosphate Regulating Neutral Endopeptidase ; Turner Syndrome*

OBJECTIVETo identify potential mutation of PHEX gene in two patients from a family affected with X-linked hypophosphatemia (XLH).

METHODSPCR and Sanger sequencing were performed on blood samples from the patients and 100 healthy controls. Reverse transcription-PCR (RT-PCR) was used to determine the mRNA expression in patient samples.

RESULTSA splicing site mutation, IVS21+2T>G, was found in the PHEX gene in both patients but not among the 100 healthy controls. RT-PCR confirmed that exon 21 of the PHEX gene was deleted.

CONCLUSIONThe novel splicing mutation IVS21+2T>G of the PHEX gene probably underlies the XLH in this pedigree. At the mRNA level, the mutation has led to removal of exon 21 and shift of the open reading frame (p.Val691fsx), resulting in premature termination of protein translation.

Adult ; Base Sequence ; DNA Mutational Analysis ; Exons ; Familial Hypophosphatemic Rickets ; genetics ; Female ; Genetic Diseases, X-Linked ; genetics ; Humans ; Male ; Middle Aged ; Molecular Sequence Data ; Mutation ; PHEX Phosphate Regulating Neutral Endopeptidase ; genetics ; Pedigree ; RNA Splicing ; Young Adult