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Toshiro Fujita - One of the best experts on this subject based on the ideXlab platform.
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mutational analysis of patients with fgf23 related Hypophosphatemic Rickets
European Journal of Endocrinology, 2012Co-Authors: Yuka Kinoshita, T Saito, Yuichiro Shimizu, Michiko Hori, Manabu Taguchi, Takashi Igarashi, Seiji Fukumoto, Toshiro FujitaAbstract:Objective: X-linked Hypophosphatemic Rickets (XLHR) caused by mutations in the PHEX gene is considered to be the most frequent cause of fibroblast growth factor 23 (FGF23)-related congenital Hypophosphatemic Rickets. In previous studies, mutations in the PHEX gene were detected in 60‐70% of patients with clinical diagnoses of XLHR. This leads to the question whether current screening methods for mutations in the PHEX gene are inadequate or whether there is a substantial number of patients with other genetic causes of Hypophosphatemic Rickets. We conducted a genetic analysis of patients with FGF23-related Hypophosphatemic Rickets to clarify their etiology and evaluate the prevalence of XLHR among this group. Design and methods: We studied 27 patients with familial and sporadic congenital Hypophosphatemic Rickets in whom serum FGF23 was above 30 pg/ml using an assay for the full-length protein. Exons and exon‐intron junctions of genomic DNA of causative genes for FGF23-related Hypophosphatemic Rickets were sequenced. PHEX mRNA from peripheral blood was analyzed in some patients. Results: Direct sequencing of genomic DNA identified 11 novel and four known mutations in the PHEX gene. Additionally, there was a large PHEX gene deletion in one case and abnormal PHEX mRNA splicing in another. In summary, 26 patients (96%) had XLHR and one patient had autosomal recessive Hypophosphatemic Rickets 2. Conclusions: XLHR is by far the most prevalent cause of FGF23-related Hypophosphatemic Rickets. We propose that analysis of PHEX mRNA from peripheral blood would be appropriate for the first screening step in determining the etiology of FGF23-related Hypophosphatemic Rickets.
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familial Hypophosphatemic Rickets caused by a large deletion in phex gene
European Journal of Endocrinology, 2009Co-Authors: T Saito, Takashi Igarashi, Seiji Fukumoto, Yutaka Nishii, Toshiyuki Yasuda, Hisanori Suzuki, Toshiro FujitaAbstract:Context: X-linked Hypophosphatemic Rickets/osteomalacia (XLH), autosomal dominant and recessive Hypophosphatemic Rickets/osteomalacia (ADHR and ARHR) share common clinical features including high fibroblast growth factor 23 (FGF23) levels. These diseases are caused by mutations in phosphate regulating endopeptidase homolog, X-linked (PHEX),FGF23, and dentin matrix acidic phosphoprotein 1 (DMP1) gene respectively. It remains unclear whether these diseases can be clinically discriminated. Objective: To clarify the underlying mechanism of patients with Hypophosphatemic Rickets whose parents showed no physical findings suggesting Rickets. Design and patients: The proband is a 39-year-old woman. She and her 37-year-old brother show the same clinical features such as bowing of legs together with hypophosphatemia (sister: P 1.8 mg/dl, brother: P 1.6 mg/dl) and high FGF23 levels (sister: 542 pg/ml, brother: 96 pg/ml). Physical findings of their parents are normal and ARHR was suspected. Results: Sequencing of all coding exons and exon‐intron junctions ofDMP1 andFGF23 genes showed no mutation. Subsequent analysis revealed that there is a deletion of 52 143 bp including exons 1‐3 in PHEX gene in the brother. His sister was found to be a heterozygote for the same deletion indicating that they are suffering from XLH. The same deletion was detected in the mother. However, the amount of the wild-type allele was more and that of the mutant one was less in genomic DNA from the mother compared with those from the sister. Single nucleotide polymorphism (SNP) analysis indicated that the mother has three kinds of PHEX alleles suggesting a somatic mosaicism. Conclusion: Careful genetic analysis is mandatory for correct differential diagnosis of Hypophosphatemic Rickets with high FGF23 levels.
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increased circulatory level of biologically active full length fgf 23 in patients with Hypophosphatemic Rickets osteomalacia
The Journal of Clinical Endocrinology and Metabolism, 2002Co-Authors: Yuji Yamazaki, Toshiro Fujita, Ryo Okazaki, Minako Shibata, Yukihiro Hasegawa, Kohei Satoh, Toshihiro Tajima, Yasuhiro Takeuchi, Kazuhiko Nakahara, Takeyoshi YamashitaAbstract:Hypophosphatemic Rickets/osteomalacia with inappropriately low serum 1,25-dihidroxyvitamin D level is commonly observed in X-linked Hypophosphatemic Rickets/osteomalacia, autosomal dominant Hypophosphatemic Rickets/osteomalacia and tumor-induced osteomalacia. Although the involvement of a newly identified factor, FGF-23, in the pathogenesis of ADHR and TIO has been suggested, clinical evidence indicating the role of FGF-23 has been lacking. We have previously shown that FGF-23 is cleaved between Arg179 and Ser180, and this processing abolished biological activity of FGF-23 to induce hypophosphatemia. Therefore, sandwich ELISA for biologically active intact human FGF-23 was developed using two kinds of monoclonal antibodies that requires the simultaneous presence of both the N-terminal and C-terminal portion of FGF-23. The serum levels of FGF-23 in healthy adults were measurable and ranged from 8.2 to 54.3 ng/L. In contrast, those in a patient with TIO were over 200 ng/L. After the resection of the respons...
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Increased Circulatory Level of Biologically Active Full-Length FGF-23 in Patients with Hypophosphatemic Rickets/Osteomalacia
The Journal of Clinical Endocrinology and Metabolism, 2002Co-Authors: Yuji Yamazaki, Toshiro Fujita, Ryo Okazaki, Minako Shibata, Yukihiro Hasegawa, Kohei Satoh, Toshihiro Tajima, Yasuhiro Takeuchi, Kazuhiko Nakahara, Takeyoshi YamashitaAbstract:Hypophosphatemic Rickets/osteomalacia with inappropriately low serum 1,25-dihidroxyvitamin D level is commonly observed in X-linked Hypophosphatemic Rickets/osteomalacia, autosomal dominant Hypophosphatemic Rickets/osteomalacia and tumor-induced osteomalacia. Although the involvement of a newly identified factor, FGF-23, in the pathogenesis of ADHR and TIO has been suggested, clinical evidence indicating the role of FGF-23 has been lacking. We have previously shown that FGF-23 is cleaved between Arg179 and Ser180, and this processing abolished biological activity of FGF-23 to induce hypophosphatemia. Therefore, sandwich ELISA for biologically active intact human FGF-23 was developed using two kinds of monoclonal antibodies that requires the simultaneous presence of both the N-terminal and C-terminal portion of FGF-23. The serum levels of FGF-23 in healthy adults were measurable and ranged from 8.2 to 54.3 ng/L. In contrast, those in a patient with TIO were over 200 ng/L. After the resection of the respons...
Hope Northrup - One of the best experts on this subject based on the ideXlab platform.
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mutational analysis of phex fgf23 and dmp1 in a cohort of patients with Hypophosphatemic Rickets
Clinical Endocrinology, 2011Co-Authors: Mary D Ruppe, Patrick G Brosnan, Kit Sing Au, Phong X Tran, Barbara W Dominguez, Hope NorthrupAbstract:Background X-linked Hypophosphatemic Rickets, autosomal dominant Hypophosphatemic Rickets and autosomal recessive Hypophosphatemic Rickets make up a group of renal phosphate wasting disorders with common clinical and biochemical characteristics. These three types of Rickets are related to mutations in PHEX, FGF23 and DMP1, respectively.
T Saito - One of the best experts on this subject based on the ideXlab platform.
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mutational analysis of patients with fgf23 related Hypophosphatemic Rickets
European Journal of Endocrinology, 2012Co-Authors: Yuka Kinoshita, T Saito, Yuichiro Shimizu, Michiko Hori, Manabu Taguchi, Takashi Igarashi, Seiji Fukumoto, Toshiro FujitaAbstract:Objective: X-linked Hypophosphatemic Rickets (XLHR) caused by mutations in the PHEX gene is considered to be the most frequent cause of fibroblast growth factor 23 (FGF23)-related congenital Hypophosphatemic Rickets. In previous studies, mutations in the PHEX gene were detected in 60‐70% of patients with clinical diagnoses of XLHR. This leads to the question whether current screening methods for mutations in the PHEX gene are inadequate or whether there is a substantial number of patients with other genetic causes of Hypophosphatemic Rickets. We conducted a genetic analysis of patients with FGF23-related Hypophosphatemic Rickets to clarify their etiology and evaluate the prevalence of XLHR among this group. Design and methods: We studied 27 patients with familial and sporadic congenital Hypophosphatemic Rickets in whom serum FGF23 was above 30 pg/ml using an assay for the full-length protein. Exons and exon‐intron junctions of genomic DNA of causative genes for FGF23-related Hypophosphatemic Rickets were sequenced. PHEX mRNA from peripheral blood was analyzed in some patients. Results: Direct sequencing of genomic DNA identified 11 novel and four known mutations in the PHEX gene. Additionally, there was a large PHEX gene deletion in one case and abnormal PHEX mRNA splicing in another. In summary, 26 patients (96%) had XLHR and one patient had autosomal recessive Hypophosphatemic Rickets 2. Conclusions: XLHR is by far the most prevalent cause of FGF23-related Hypophosphatemic Rickets. We propose that analysis of PHEX mRNA from peripheral blood would be appropriate for the first screening step in determining the etiology of FGF23-related Hypophosphatemic Rickets.
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a patient with Hypophosphatemic Rickets and ossification of posterior longitudinal ligament caused by a novel homozygous mutation in enpp1 gene
Bone, 2011Co-Authors: T Saito, Yuichiro Shimizu, Michiko Hori, Manabu Taguchi, Takashi Igarashi, Seiji Fukumoto, Toshiro FujitabAbstract:Abstract X-linked Hypophosphatemic Rickets/osteomalacia (XLH), autosomal dominant Hypophosphatemic Rickets/osteomalacia (ADHR) and autosomal recessive Hypophosphatemic Rickets/osteomalacia (ARHR1 or ARHR2) are hereditary fibroblast growth factor 23 (FGF23)-related Hypophosphatemic Rickets showing similar clinical features. We here show a patient with Hypophosphatemic Rickets and widespread ossification of posterior longitudinal ligament (OPLL). The proband is a 62-year-old female. Her parents are first cousins and showed no signs of Rickets or osteomalacia. She showed Hypophosphatemic Rickets with elevated FGF23 level and had been clinically considered to be suffering from XLH. However, direct sequencing of all coding exons and exon–intron junctions of phosphate regulating gene with homologies to endopeptidases on the X chromosome (PHEX) , FGF23 and dentin matrix protein 1 (DMP1) genes, responsible genes for XLH, ADHR and ARHR1, respectively, showed no mutation. A novel homozygous splice donor site mutation was found at the exon–intron junction of exon 21 of ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) gene responsible for ARHR2 (IVS21 + 1_3(GTA > CACC)). Subsequent analysis of mRNA revealed that this mutation caused skipping of exon 21 which created a premature stop codon in exon 22. These results indicate that genetic analysis is mandatory for the correct diagnosis of hereditary FGF23-related Hypophosphatemic Rickets. Because Enpp1 knockout mouse is a model of OPLL, this case also suggests that OPLL is associated with ARHR2.
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familial Hypophosphatemic Rickets caused by a large deletion in phex gene
European Journal of Endocrinology, 2009Co-Authors: T Saito, Takashi Igarashi, Seiji Fukumoto, Yutaka Nishii, Toshiyuki Yasuda, Hisanori Suzuki, Toshiro FujitaAbstract:Context: X-linked Hypophosphatemic Rickets/osteomalacia (XLH), autosomal dominant and recessive Hypophosphatemic Rickets/osteomalacia (ADHR and ARHR) share common clinical features including high fibroblast growth factor 23 (FGF23) levels. These diseases are caused by mutations in phosphate regulating endopeptidase homolog, X-linked (PHEX),FGF23, and dentin matrix acidic phosphoprotein 1 (DMP1) gene respectively. It remains unclear whether these diseases can be clinically discriminated. Objective: To clarify the underlying mechanism of patients with Hypophosphatemic Rickets whose parents showed no physical findings suggesting Rickets. Design and patients: The proband is a 39-year-old woman. She and her 37-year-old brother show the same clinical features such as bowing of legs together with hypophosphatemia (sister: P 1.8 mg/dl, brother: P 1.6 mg/dl) and high FGF23 levels (sister: 542 pg/ml, brother: 96 pg/ml). Physical findings of their parents are normal and ARHR was suspected. Results: Sequencing of all coding exons and exon‐intron junctions ofDMP1 andFGF23 genes showed no mutation. Subsequent analysis revealed that there is a deletion of 52 143 bp including exons 1‐3 in PHEX gene in the brother. His sister was found to be a heterozygote for the same deletion indicating that they are suffering from XLH. The same deletion was detected in the mother. However, the amount of the wild-type allele was more and that of the mutant one was less in genomic DNA from the mother compared with those from the sister. Single nucleotide polymorphism (SNP) analysis indicated that the mother has three kinds of PHEX alleles suggesting a somatic mosaicism. Conclusion: Careful genetic analysis is mandatory for correct differential diagnosis of Hypophosphatemic Rickets with high FGF23 levels.
Takashi Igarashi - One of the best experts on this subject based on the ideXlab platform.
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mutational analysis of patients with fgf23 related Hypophosphatemic Rickets
European Journal of Endocrinology, 2012Co-Authors: Yuka Kinoshita, T Saito, Yuichiro Shimizu, Michiko Hori, Manabu Taguchi, Takashi Igarashi, Seiji Fukumoto, Toshiro FujitaAbstract:Objective: X-linked Hypophosphatemic Rickets (XLHR) caused by mutations in the PHEX gene is considered to be the most frequent cause of fibroblast growth factor 23 (FGF23)-related congenital Hypophosphatemic Rickets. In previous studies, mutations in the PHEX gene were detected in 60‐70% of patients with clinical diagnoses of XLHR. This leads to the question whether current screening methods for mutations in the PHEX gene are inadequate or whether there is a substantial number of patients with other genetic causes of Hypophosphatemic Rickets. We conducted a genetic analysis of patients with FGF23-related Hypophosphatemic Rickets to clarify their etiology and evaluate the prevalence of XLHR among this group. Design and methods: We studied 27 patients with familial and sporadic congenital Hypophosphatemic Rickets in whom serum FGF23 was above 30 pg/ml using an assay for the full-length protein. Exons and exon‐intron junctions of genomic DNA of causative genes for FGF23-related Hypophosphatemic Rickets were sequenced. PHEX mRNA from peripheral blood was analyzed in some patients. Results: Direct sequencing of genomic DNA identified 11 novel and four known mutations in the PHEX gene. Additionally, there was a large PHEX gene deletion in one case and abnormal PHEX mRNA splicing in another. In summary, 26 patients (96%) had XLHR and one patient had autosomal recessive Hypophosphatemic Rickets 2. Conclusions: XLHR is by far the most prevalent cause of FGF23-related Hypophosphatemic Rickets. We propose that analysis of PHEX mRNA from peripheral blood would be appropriate for the first screening step in determining the etiology of FGF23-related Hypophosphatemic Rickets.
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a patient with Hypophosphatemic Rickets and ossification of posterior longitudinal ligament caused by a novel homozygous mutation in enpp1 gene
Bone, 2011Co-Authors: T Saito, Yuichiro Shimizu, Michiko Hori, Manabu Taguchi, Takashi Igarashi, Seiji Fukumoto, Toshiro FujitabAbstract:Abstract X-linked Hypophosphatemic Rickets/osteomalacia (XLH), autosomal dominant Hypophosphatemic Rickets/osteomalacia (ADHR) and autosomal recessive Hypophosphatemic Rickets/osteomalacia (ARHR1 or ARHR2) are hereditary fibroblast growth factor 23 (FGF23)-related Hypophosphatemic Rickets showing similar clinical features. We here show a patient with Hypophosphatemic Rickets and widespread ossification of posterior longitudinal ligament (OPLL). The proband is a 62-year-old female. Her parents are first cousins and showed no signs of Rickets or osteomalacia. She showed Hypophosphatemic Rickets with elevated FGF23 level and had been clinically considered to be suffering from XLH. However, direct sequencing of all coding exons and exon–intron junctions of phosphate regulating gene with homologies to endopeptidases on the X chromosome (PHEX) , FGF23 and dentin matrix protein 1 (DMP1) genes, responsible genes for XLH, ADHR and ARHR1, respectively, showed no mutation. A novel homozygous splice donor site mutation was found at the exon–intron junction of exon 21 of ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) gene responsible for ARHR2 (IVS21 + 1_3(GTA > CACC)). Subsequent analysis of mRNA revealed that this mutation caused skipping of exon 21 which created a premature stop codon in exon 22. These results indicate that genetic analysis is mandatory for the correct diagnosis of hereditary FGF23-related Hypophosphatemic Rickets. Because Enpp1 knockout mouse is a model of OPLL, this case also suggests that OPLL is associated with ARHR2.
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familial Hypophosphatemic Rickets caused by a large deletion in phex gene
European Journal of Endocrinology, 2009Co-Authors: T Saito, Takashi Igarashi, Seiji Fukumoto, Yutaka Nishii, Toshiyuki Yasuda, Hisanori Suzuki, Toshiro FujitaAbstract:Context: X-linked Hypophosphatemic Rickets/osteomalacia (XLH), autosomal dominant and recessive Hypophosphatemic Rickets/osteomalacia (ADHR and ARHR) share common clinical features including high fibroblast growth factor 23 (FGF23) levels. These diseases are caused by mutations in phosphate regulating endopeptidase homolog, X-linked (PHEX),FGF23, and dentin matrix acidic phosphoprotein 1 (DMP1) gene respectively. It remains unclear whether these diseases can be clinically discriminated. Objective: To clarify the underlying mechanism of patients with Hypophosphatemic Rickets whose parents showed no physical findings suggesting Rickets. Design and patients: The proband is a 39-year-old woman. She and her 37-year-old brother show the same clinical features such as bowing of legs together with hypophosphatemia (sister: P 1.8 mg/dl, brother: P 1.6 mg/dl) and high FGF23 levels (sister: 542 pg/ml, brother: 96 pg/ml). Physical findings of their parents are normal and ARHR was suspected. Results: Sequencing of all coding exons and exon‐intron junctions ofDMP1 andFGF23 genes showed no mutation. Subsequent analysis revealed that there is a deletion of 52 143 bp including exons 1‐3 in PHEX gene in the brother. His sister was found to be a heterozygote for the same deletion indicating that they are suffering from XLH. The same deletion was detected in the mother. However, the amount of the wild-type allele was more and that of the mutant one was less in genomic DNA from the mother compared with those from the sister. Single nucleotide polymorphism (SNP) analysis indicated that the mother has three kinds of PHEX alleles suggesting a somatic mosaicism. Conclusion: Careful genetic analysis is mandatory for correct differential diagnosis of Hypophosphatemic Rickets with high FGF23 levels.
Seiji Fukumoto - One of the best experts on this subject based on the ideXlab platform.
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mutational analysis of patients with fgf23 related Hypophosphatemic Rickets
European Journal of Endocrinology, 2012Co-Authors: Yuka Kinoshita, T Saito, Yuichiro Shimizu, Michiko Hori, Manabu Taguchi, Takashi Igarashi, Seiji Fukumoto, Toshiro FujitaAbstract:Objective: X-linked Hypophosphatemic Rickets (XLHR) caused by mutations in the PHEX gene is considered to be the most frequent cause of fibroblast growth factor 23 (FGF23)-related congenital Hypophosphatemic Rickets. In previous studies, mutations in the PHEX gene were detected in 60‐70% of patients with clinical diagnoses of XLHR. This leads to the question whether current screening methods for mutations in the PHEX gene are inadequate or whether there is a substantial number of patients with other genetic causes of Hypophosphatemic Rickets. We conducted a genetic analysis of patients with FGF23-related Hypophosphatemic Rickets to clarify their etiology and evaluate the prevalence of XLHR among this group. Design and methods: We studied 27 patients with familial and sporadic congenital Hypophosphatemic Rickets in whom serum FGF23 was above 30 pg/ml using an assay for the full-length protein. Exons and exon‐intron junctions of genomic DNA of causative genes for FGF23-related Hypophosphatemic Rickets were sequenced. PHEX mRNA from peripheral blood was analyzed in some patients. Results: Direct sequencing of genomic DNA identified 11 novel and four known mutations in the PHEX gene. Additionally, there was a large PHEX gene deletion in one case and abnormal PHEX mRNA splicing in another. In summary, 26 patients (96%) had XLHR and one patient had autosomal recessive Hypophosphatemic Rickets 2. Conclusions: XLHR is by far the most prevalent cause of FGF23-related Hypophosphatemic Rickets. We propose that analysis of PHEX mRNA from peripheral blood would be appropriate for the first screening step in determining the etiology of FGF23-related Hypophosphatemic Rickets.
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a patient with Hypophosphatemic Rickets and ossification of posterior longitudinal ligament caused by a novel homozygous mutation in enpp1 gene
Bone, 2011Co-Authors: T Saito, Yuichiro Shimizu, Michiko Hori, Manabu Taguchi, Takashi Igarashi, Seiji Fukumoto, Toshiro FujitabAbstract:Abstract X-linked Hypophosphatemic Rickets/osteomalacia (XLH), autosomal dominant Hypophosphatemic Rickets/osteomalacia (ADHR) and autosomal recessive Hypophosphatemic Rickets/osteomalacia (ARHR1 or ARHR2) are hereditary fibroblast growth factor 23 (FGF23)-related Hypophosphatemic Rickets showing similar clinical features. We here show a patient with Hypophosphatemic Rickets and widespread ossification of posterior longitudinal ligament (OPLL). The proband is a 62-year-old female. Her parents are first cousins and showed no signs of Rickets or osteomalacia. She showed Hypophosphatemic Rickets with elevated FGF23 level and had been clinically considered to be suffering from XLH. However, direct sequencing of all coding exons and exon–intron junctions of phosphate regulating gene with homologies to endopeptidases on the X chromosome (PHEX) , FGF23 and dentin matrix protein 1 (DMP1) genes, responsible genes for XLH, ADHR and ARHR1, respectively, showed no mutation. A novel homozygous splice donor site mutation was found at the exon–intron junction of exon 21 of ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) gene responsible for ARHR2 (IVS21 + 1_3(GTA > CACC)). Subsequent analysis of mRNA revealed that this mutation caused skipping of exon 21 which created a premature stop codon in exon 22. These results indicate that genetic analysis is mandatory for the correct diagnosis of hereditary FGF23-related Hypophosphatemic Rickets. Because Enpp1 knockout mouse is a model of OPLL, this case also suggests that OPLL is associated with ARHR2.
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familial Hypophosphatemic Rickets caused by a large deletion in phex gene
European Journal of Endocrinology, 2009Co-Authors: T Saito, Takashi Igarashi, Seiji Fukumoto, Yutaka Nishii, Toshiyuki Yasuda, Hisanori Suzuki, Toshiro FujitaAbstract:Context: X-linked Hypophosphatemic Rickets/osteomalacia (XLH), autosomal dominant and recessive Hypophosphatemic Rickets/osteomalacia (ADHR and ARHR) share common clinical features including high fibroblast growth factor 23 (FGF23) levels. These diseases are caused by mutations in phosphate regulating endopeptidase homolog, X-linked (PHEX),FGF23, and dentin matrix acidic phosphoprotein 1 (DMP1) gene respectively. It remains unclear whether these diseases can be clinically discriminated. Objective: To clarify the underlying mechanism of patients with Hypophosphatemic Rickets whose parents showed no physical findings suggesting Rickets. Design and patients: The proband is a 39-year-old woman. She and her 37-year-old brother show the same clinical features such as bowing of legs together with hypophosphatemia (sister: P 1.8 mg/dl, brother: P 1.6 mg/dl) and high FGF23 levels (sister: 542 pg/ml, brother: 96 pg/ml). Physical findings of their parents are normal and ARHR was suspected. Results: Sequencing of all coding exons and exon‐intron junctions ofDMP1 andFGF23 genes showed no mutation. Subsequent analysis revealed that there is a deletion of 52 143 bp including exons 1‐3 in PHEX gene in the brother. His sister was found to be a heterozygote for the same deletion indicating that they are suffering from XLH. The same deletion was detected in the mother. However, the amount of the wild-type allele was more and that of the mutant one was less in genomic DNA from the mother compared with those from the sister. Single nucleotide polymorphism (SNP) analysis indicated that the mother has three kinds of PHEX alleles suggesting a somatic mosaicism. Conclusion: Careful genetic analysis is mandatory for correct differential diagnosis of Hypophosphatemic Rickets with high FGF23 levels.