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A Novel PHEX Gene Mutation in a Patient with Sporadic Hypophosphatemic Rickets.

ABSTRACT: Phosphate regulating gene with homologies to endopeptidases on the X-chromosome (PHEX) is a common cause of X-linked hypophosphatemic (XLH) rickets. Diverse PHEX gene mutations have been reported; however, gene mutations in sporadic rickets are less common than in XLH rickets. Herein, we describe a 50-year-old female patient with sporadic hypophosphatemic rickets harboring a novel splicing-site mutation in the PHEX gene (c.663+1G>A) at the exon 5-intron 5 boundary. The patient had recently suffered from right thigh pain and an aggravated waddling gait. She also presented with very short stature, generalized bone pain, and muscle weakness. Despite low serum phosphate levels, her phosphate reabsorption rate was lower than normal. Additionally, her 1,25-dihydroxyvitamin D3 concentration was lower than normal, although FGF23 level was normal. After treatment with alfacalcidol and elemental phosphate, her rachitic symptoms subsided, and callus formation was observed in the fracture site on the right femur.

SUBMITTER: Kang YE

PROVIDER: S-EPMC4091495 | biostudies-literature | 2014 Jun

REPOSITORIES: biostudies-literature

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A Novel PHEX Gene Mutation in a Patient with Sporadic Hypophosphatemic Rickets.

Kang Yea Eun YE Hong Jun Hwa JH Kim Jimin J Joung Kyong Hye KH Kim Hyun Jin HJ Ku Bon Jeong BJ Kim Koon Soon KS

Endocrinology and metabolism (Seoul, Korea) 20140626 2

Phosphate regulating gene with homologies to endopeptidases on the X-chromosome (PHEX) is a common cause of X-linked hypophosphatemic (XLH) rickets. Diverse PHEX gene mutations have been reported; however, gene mutations in sporadic rickets are less common than in XLH rickets. Herein, we describe a 50-year-old female patient with sporadic hypophosphatemic rickets harboring a novel splicing-site mutation in the PHEX gene (c.663+1G>A) at the exon 5-intron 5 boundary. The patient had recently suffe ...[more]

PMID: 25031893

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Project description:ObjectiveHypophosphatemic rickets (HR) is a heterogeneous genetic phosphate wasting disorder. The disease is most commonly caused by mutations in the PHEX gene located on the X-chromosome or by mutations in CLCN5, DMP1, ENPP1, FGF23, and SLC34A3. The aims of this study were to perform molecular diagnostics for four patients with HR of Indian origin (two independent families) and to describe their clinical features.MethodsWe performed whole exome sequencing (WES) for the affected mother of two boys who also displayed the typical features of HR, including bone malformations and phosphate wasting. B-lymphoblast cell lines were established by EBV transformation and subsequent RT-PCR to investigate an uncommon splice site variant found by WES. An in silico analysis was done to obtain accurate nucleotide frequency occurrences of consensus splice positions other than the canonical sites of all human exons. Additionally, we applied direct Sanger sequencing for all exons and exon/intron boundaries of the PHEX gene for an affected girl from an independent second Indian family.ResultsWES revealed a novel PHEX splice acceptor mutation in intron 9 (c.1080-3C>A) in a family with 3 affected individuals with HR. The effect on splicing of this mutation was further investigated by RT-PCR using RNA obtained from a patient's EBV-transformed lymphoblast cell line. RT-PCR revealed an aberrant splice transcript skipping exons 10-14 which was not observed in control samples, confirming the diagnosis of X-linked dominant hypophosphatemia (XLH). The in silico analysis of all human splice sites adjacent to all 327,293 exons across 81,814 transcripts among 20,345 human genes revealed that cytosine is, with 64.3%, the most frequent nucleobase at the minus 3 splice acceptor position, followed by thymidine with 28.7%, adenine with 6.3%, and guanine with 0.8%. We generated frequency tables and pictograms for the extended donor and acceptor splice consensus regions by analyzing all human exons. Direct Sanger sequencing of all PHEX exons in a sporadic case with HR from the Indian subcontinent revealed an additional novel PHEX mutation (c.1211_1215delACAAAinsTTTACAT, p.Asp404Valfs*5, de novo) located in exon 11.ConclusionsMutation analyses revealed two novel mutations and helped to confirm the clinical diagnoses of XLH in two families from India. WES helped to analyze all genes implicated in the underlying disease complex. Mutations at splice positions other than the canonical key sites need further functional investigation to support the assertion of pathogenicity.

Dataset Information

A Novel PHEX Gene Mutation in a Patient with Sporadic Hypophosphatemic Rickets.

Publications

A Novel PHEX Gene Mutation in a Patient with Sporadic Hypophosphatemic Rickets.

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