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Poon KS, Tan KML, Zacharin M, Ho CWL. A De Novo Mosaic PHEX Variant Causing Sporadic X-Linked Hypophosphatemic Rickets in a 2-Year-Old Girl. J Pediatr Genet 2023; 12:308-311. [PMID: 38162152 PMCID: PMC10756725 DOI: 10.1055/s-0041-1728746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/11/2021] [Indexed: 10/21/2022]
Abstract
Pathogenic variants in the PHEX gene are causative of X-linked hypophosphatemic rickets (XLH). We present a case of a 2-year-old girl with hypophosphatemic rickets with genu varum and short stature without any family history of XLH. Next generation sequencing of the PHEX gene identified a splice donor variant, NM_000444.6:c.1173 + 5G > A in intron 10. This variant had a mosaic pattern with only 22% of the sequence reads showing the variant allele and was not present in the girl's parents, both of whom had a normal phenotype. This is a sporadic case of a de novo mosaic splice-site variant in the PHEX gene.
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Affiliation(s)
- Kok-Siong Poon
- Department of Laboratory Medicine, National University Hospital, Singapore
| | - Karen Mei-Ling Tan
- Department of Laboratory Medicine, National University Hospital, Singapore
| | - Margaret Zacharin
- Department of Hormone Research, Murdoch Children's Research Institute, Melbourne, Australia
- Department of Paediatrics, University of Melbourne, Victoria, Australia
- Department of Endocrinology & Diabetes, The Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Cindy Wei-Li Ho
- Department of Paediatrics, Khoo Teck Puat - National University Children's Medical Institute, National University Health System, Singapore
- Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Lin Y, Zhang W, Huang X, Su L, Cai Y, Liang C, Rao M, Liu L, Zeng C. Two De Novo Mosaic Variants Within the Same Site of PHEX Gene in a Girl with X-Linked Hypophosphatemic Rickets. Calcif Tissue Int 2022; 110:266-271. [PMID: 34487203 DOI: 10.1007/s00223-021-00909-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 08/22/2021] [Indexed: 10/20/2022]
Abstract
X-linked hypophosphatemic rickets (XLH) is the most common form of hypophosphatemic rickets, which is caused by the deficiencies of PHEX gene with an X-linked dominant inheritance pattern. As at least several thousands of XLH patients have been diagnosed, only several males and fewer females with mosaicism of PHEX gene were found. Here we describe an XLH girl with two de novo mosaic variants within the same site of PHEX gene. To rapidly screen all of the causative genes of hypophosphatemic rickets and rule out other diseases, DNA samples were initially analyzed using whole exome sequencing (WES). Interestingly, two different pathogenic mosaic variants, a known c.1809G > A(p.W603*) variant and a novel c.1809G > T(p.W603C) variant within the same site of PHEX gene, were identified in the proband by WES. Subsequent Sanger sequencing confirmed the presence and de novo pattern of these two mosaic variants in the proband, which were absent in her healthy parents. This is the first case to report two different mosaic variants of PHEX gene in an XLH individual. This XLH girl has a de novo mosaic genotype of c.1809 = /G > T/G > A in PHEX gene. Our report adds an unusual mocaicism case for XLH and expands the mutational event and spectrum of PHEX gene. Our report also alerts clinicians and geneticists to be cautious about mocaicism and detection methods.
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Affiliation(s)
- Yunting Lin
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, 9 Jinsui Rd., Guangzhou, 510623, China
| | - Wen Zhang
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, 9 Jinsui Rd., Guangzhou, 510623, China
| | - Xinjiang Huang
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, 9 Jinsui Rd., Guangzhou, 510623, China
| | - Ling Su
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, 9 Jinsui Rd., Guangzhou, 510623, China
| | - Yanna Cai
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, 9 Jinsui Rd., Guangzhou, 510623, China
| | - Cuili Liang
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, 9 Jinsui Rd., Guangzhou, 510623, China
| | - Min Rao
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, 9 Jinsui Rd., Guangzhou, 510623, China
| | - Li Liu
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, 9 Jinsui Rd., Guangzhou, 510623, China.
| | - Chunhua Zeng
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, 9 Jinsui Rd., Guangzhou, 510623, China.
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Asano S, Sako S, Funasaki Y, Takeshita Y, Niida Y, Takamura T. A mosaic mutation of phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX) in X-linked hypophosphatemic rickets with mild bone phenotypes. Endocr J 2021; 68:1135-1141. [PMID: 33907069 DOI: 10.1507/endocrj.ej20-0809] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
X-linked hypophosphatemic rickets (XLH) is primarily characterized by renal phosphate wasting with hypophosphatemia, short stature, and bone deformity of the leg. Here we present a male case of XLH with relatively mild bone deformity caused by a mosaic mutation of the phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX). Polymerase chain reaction (PCR) direct sequencing revealed a novel in-frame deletion, NM-000444.6:c.671-685del p.Gln224-Ser228del, at exon 6 in PHEX as a mosaic pattern. This mutation was not found in any database and may result in a significant change in higher-order protein structure and function. TA cloning of the PCR product and clone sequencing estimated the mutation allele frequency at 21%. Literature review of the previously reported three cases with novel mosaic mutations in PHEX, together with the present case, suggests that the rates of the mutation allele correlate with phenotype severity to some extent. We initially treated him with nutritional vitamin D supplements and phosphate salts. However, to avoid the development of secondary/tertiary hyperparathyroidism, we had switched nutritional to active vitamin D supplementation with reduced phosphorus salts. The present report contributes to understanding the relationship between the mosaic rate, in addition to the mutation locus, of the PHEX gene, and clinical features of XLH.
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Affiliation(s)
- Shoko Asano
- Department of Endocrinology and Metabolism, Kanazawa University Graduate School of Medical Sciences, Ishikawa 920-8640, Japan
| | - Saori Sako
- Department of Endocrinology and Metabolism, Kanazawa University Graduate School of Medical Sciences, Ishikawa 920-8640, Japan
| | - Yuka Funasaki
- Department of Endocrinology and Metabolism, Kanazawa University Graduate School of Medical Sciences, Ishikawa 920-8640, Japan
| | - Yumie Takeshita
- Department of Endocrinology and Metabolism, Kanazawa University Graduate School of Medical Sciences, Ishikawa 920-8640, Japan
| | - Yo Niida
- Division of Genomic Medicine, Department of Advanced Medicine, Medical Research Institute, Kanazawa Medical University, Ishikawa 920-0293, Japan
| | - Toshinari Takamura
- Department of Endocrinology and Metabolism, Kanazawa University Graduate School of Medical Sciences, Ishikawa 920-8640, Japan
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Thiele S, Werner R, Stubbe A, Hiort O, Hoeppner W. Validation of a next-generation sequencing (NGS) panel to improve the diagnosis of X-linked hypophosphataemia (XLH) and other genetic disorders of renal phosphate wasting. Eur J Endocrinol 2020; 183:497-504. [PMID: 33107440 PMCID: PMC7592643 DOI: 10.1530/eje-20-0275] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 08/14/2020] [Indexed: 01/03/2023]
Abstract
BACKGROUND Hypophosphataemic rickets (HR) comprise a clinically and genetically heterogeneous group of conditions, defined by renal-tubular phosphate wasting and consecutive loss of bone mineralisation. X-linked hypophosphataemia (XLH) is the most common form, caused by inactivating dominant mutations in PHEX, a gene encompassing 22 exons located at Xp22.1. XLH is treatable by anti-Fibroblast Growth Factor 23 antibody, while for other forms of HR such as therapy may not be indicated. Therefore, a genetic differentiation of HR is recommended. OBJECTIVE To develop and validate a next-generation sequencing panel for HR with special focus on PHEX. DESIGN AND METHODS We designed an AmpliSeq gene panel for the IonTorrent PGM next-generation platform for PHEX and ten other HR-related genes. For validation of PHEX sequencing 50 DNA-samples from XLH-patients, in whom 42 different mutations in PHEX and 1 structural variation have been proven before, were blinded, anonymised and investigated with the NGS panel. In addition, we analyzed one known homozygous DMP1 mutation and two samples of HR-patients, where no pathogenic PHEX mutation had been detected by conventional sequencing. RESULTS The panel detected all 42 pathogenic missense/nonsense/splice-site/indel PHEX-mutations and in one the known homozygous DMP1 mutation. In the remaining two patients, we revealed a somatic mosaicism of a PHEX mutation in one; as well as two variations in DMP1 and a very rare compound heterozygous variation in ENPP1 in the second patient. CONCLUSIONS This developed NGS panel is a reliable tool with high sensitivity and specificity for the diagnosis of XLH and related forms of HR.
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Affiliation(s)
- Susanne Thiele
- Division of Paediatric Endocrinology and Diabetes, Department of Pediatrics, University of Lübeck, Lübeck, Germany
| | - Ralf Werner
- Division of Paediatric Endocrinology and Diabetes, Department of Pediatrics, University of Lübeck, Lübeck, Germany
- Institute for Molecular Medicine, University of Lübeck, Lübeck, Germany
| | - Annika Stubbe
- Labor Dr. Heidrich und Kollegen MVZ GmbH, Hamburg, Germany
| | - Olaf Hiort
- Division of Paediatric Endocrinology and Diabetes, Department of Pediatrics, University of Lübeck, Lübeck, Germany
- Correspondence should be addressed to O Hiort;
| | - Wolfgang Hoeppner
- Labor Dr. Heidrich und Kollegen MVZ GmbH, Hamburg, Germany
- Bioglobe GmbH, Hamburg, Germany
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Jo HY, Shin JH, Kim HY, Kim YM, Lee H, Bae MH, Park KH, Jang JH, Kwak MJ. Identification of a novel variant in the PHEX gene using targeted gene panel sequencing in a 24-month-old boy with hypophosphatemic rickets. Ann Pediatr Endocrinol Metab 2020; 25:63-67. [PMID: 32252220 PMCID: PMC7136512 DOI: 10.6065/apem.2020.25.1.63] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 05/31/2019] [Indexed: 12/15/2022] Open
Abstract
Familial hypophosphatemic rickets (FHR) is a disorder characterized by phosphate wasting and hypophosphatemia due to defects in renal phosphate transport regulation. There are 4 known inherited forms of FHR that differ in their molecular causes. Very few studies have been conducted that focused on the molecular analysis of FHR in Koreans. Eighteen mutations of the PHEX gene have been identified to this date in Korea. Herein, we report the clinical case of a 24-month-old boy presenting with bowed legs and short stature. The biochemical profile showed hypophosphatemia with decreased tubular reabsorption of phosphate. Several family members were identified with short stature and genu varum. Therefore, he was diagnosed with FHR. To identify the molecular causes of FHR, we performed targeted gene panel sequencing and found a novel hemizygous missense variant, c.1949T>C (p.Leu650Pro), in the PHEX gene. This variant was also detected in the boy's mother who exhibited genu varum and short stature.
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Affiliation(s)
- Ha Young Jo
- Department of Pediatrics, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea
| | - Jung Hyun Shin
- Department of Pediatrics, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea
| | - Hye Young Kim
- Department of Pediatrics, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea
| | - Young Mi Kim
- Department of Pediatrics, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea
| | - Heirim Lee
- Department of Pediatrics, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea
| | - Mi Hye Bae
- Department of Pediatrics, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea
| | - Kyung Hee Park
- Department of Pediatrics, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea
| | | | - Min Jung Kwak
- Department of Pediatrics, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea,Address for correspondence: Min Jung Kwak, MD, PhD Department of Pediatrics, Pusan National University Hospital, 179 Gudeok-ro, Seo-gu, Busan 49241, Korea Tel: +82-51-240-7298 Fax: +82-51-248-6205 E-mail:
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