Mineralization Defects in the Primary Dentition Associated With X-Linked Hypophosphatemic Rickets.
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ABSTRACT:
SUBMITTER: Clayton D
PROVIDER: S-EPMC8046057 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundX-linked hypophosphatemic rickets (XLH) is the first cause of inherited hypophosphatemia and is caused by mutation in the PHEX gene, resulting in excessive expression of the phosphaturic factor FGF23. Symptoms are mainly related to rickets in children and osteomalacia in adults and cause several complications that can be highly invalidating. Due to its rarity, XLH is poorly known and diagnosis is frequently delayed. Conventional treatment is based on oral phosphate salts supplementation and activated vitamin D analogs, which however, cannot cure the disease in most cases.ObjectiveDue to the low prevalence of XLH, an experts' opinion survey was conducted across Italian centers to collect data on XLH and on its management.MethodsA questionnaire was developed by a group of experts to collect data on XLH epidemiology, diagnosis and treatment in Italy.ResultsData from 10 Italian centers (nine of which pediatric) on 175 patients, followed between 1998 and 2017, were included in the survey. Most patients were followed since childhood and 63 children became adults during the investigated period. The diagnosis was made before the age of 1 and between 1 and 5 years in 11 and 50% of cases, respectively. Clinically apparent bone deformities were present in 95% of patients. These were ranked moderate/severe in 75% of subjects and caused growth stunting in 67% of patients. Other frequent complications included bone pain (40%), dental abscesses (33%), and dental malpositions (53%). Treatment protocols varied substantially among centers. Nephrocalcinosis was observed in 34% of patients. Tertiary hyperparathyroidism developed in 6% of patients.ConclusionsXLH remains a severe condition with significant morbidities.
| S-EPMC6545008 | biostudies-literature
Project description:Autosomal dominant hypophosphatemic rickets (ADHR) is an inherited disorder of isolated renal phosphate wasting, the pathogenesis of which is unknown. We performed a genome-wide linkage study in a large kindred to determine the chromosome location of the ADHR gene. Two-point LOD scores indicate that the gene is linked to the markers D12S314 [Z(theta) = 3.15 at theta = 0.0], vWf [Z(theta) = 5.32 at theta = 0.0], and CD4 [Z(theta) = 3.53 at theta = 0.0]. Moreover, multilocus analysis indicates that the ADHR gene locus is located on chromosome 12p13 in the 18-cM interval between the flanking markers D12S100 and D12S397. These data are the first to establish a chromosomal location for the ADHR locus and to provide a framework map to further localize the gene. Such studies will permit ultimate identification of the ADHR gene and provide further insight into phosphate homeostasis.
| S-EPMC508467 | biostudies-other
Project description:X-linked hypophosphatemic rickets (XLH) is the commonest inherited form of rickets. It is caused by an impaired regulation of fibroblast growth factor 23 (FGF23) due to a PHEX gene mutation, which leads to reduced tubular reabsorption of phosphate and renal 1α-hydroxylase activity and increased renal 24-hydroxylase activity. Hypophosphatemia associated with renal phosphate wasting, normal serum levels of calcium, parathyroid hormone, and 25-hydroxyvitamin D represents the main biochemical sign in affected patients. Patients with XLH show rickets and osteomalacia, severe deformities of the lower limbs, bone and muscular pain, stunted growth, and reduced quality of life. However, XLH is a multisystemic disorder requiring multidisciplinary approaches in specialized subdisciplines. Severe complications may occur in patients with XLH including craniosynostosis, hearing loss, progressive bone deformities, dental and periodontal recurrent lesions, and psychosocial distress. Moreover, long-term conventional treatment with active vitamin D metabolites and oral inorganic phosphate salts may cause endocrinological complications such as secondary or tertiary hyperparathyroidism, and adverse events in kidney as hypercalciuria, nephrocalcinosis, and nephrolithiasis. However, conventional treatment does not improve phosphate metabolism and it shows poor and slow effects in improving rickets lesions and linear growth. Recently, some trials of treatment with recombinant human IgG1 monoclonal antibody that targets FGF23 (burosumab) showed significant improvement of serum phosphate concentration and renal tubular reabsorption of phosphate that were associated with a rapid healing of radiologic signs of rickets, reduced muscular and osteoarticular pain, and improved physical function, being more effective for the treatment of patients with XLH in comparison with conventional therapy. Therefore, a global management of patients with XLH is strongly recommended and patients should be seen regularly by a multidisciplinary team of experts.
| S-EPMC8378329 | biostudies-literature
Project description:Hypophosphatemic rickets is a rare form of rickets that affect children. The diagnosis requires high index of suspicion. We report a case of Hypophosphatemic rickets in 18-month-old Saudi boy presented with delayed walking and lower limb deformity. The diagnosis was confirmed by bone profile, radiological study and genetic testing, which reveled PHEX mutation. The patient was successfully treated by phosphate supplement.
| S-EPMC5621863 | biostudies-literature
Project description:X‑linked hypophosphatemic rickets (XLH, OMIM #307800) is a rare genetic metabolic disorder caused by dysregulation of fibroblast-like growth factor 23 (FGF23) leading to profound reduction in renal phosphate reabsorption. Impaired growth, severe rickets and complex skeletal deformities are direct consequences of hypophosphatemia representing major symptoms of XLH during childhood. In adults, secondary complications including early development of osteoarthritis substantially impair quality of life and cause significant clinical burden. With the global approval of the monoclonal FGF23 antibody burosumab, a targeted treatment with promising results in phase III studies is available for children with XLH. Nevertheless, complete phenotypic rescue is rarely achieved and remaining multisystemic symptoms demand multidisciplinary specialist care. Coordination of patient management within the major medical disciplines is a mainstay to optimize treatment and reduce disease burden. This review aims to depict different perspectives in XLH patient care in the setting of a multidisciplinary centre of expertise for rare bone diseases.
| S-EPMC7098922 | biostudies-literature
Project description:X-linked hypophosphatemic rickets (XLH) is a dominant inherited disorder characterized by renal phosphate wasting, aberrant vitamin D metabolism, and abnormal bone mineralization. Inactivating mutations in the gene encoding phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX) have been found to be associated with XLH. Here, we report a 16-year-old female patient affected by hypophosphatemic rickets. We evaluated her serum fibroblast growth factor 23 (FGF23) levels and conducted sequence analysis of the disease-associated genes of FGF23-related hypophosphatemic rickets: PHEX, FGF23, dentin matrix protein 1, and ectonucleotide pyrophosphatase/phosphodiesterase 1. She was diagnosed with XLH based on her clinical features and family history. Additionally, we observed elevated FGF23 levels and a novel PHEX exon 9 mutation (c.947G>T; p.Gly316Val) inherited from her father. Although bioinformatics showed that the mutation was neutral, Gly316 is perfectly conserved among humans, mice, and rats, and there were no mutations in other FGF23-related rickets genes, suggesting that in silico analysis is limited in determining mutation pathogenicity. In summary, we present a female patient and her father with XLH harboring a novel PHEX mutation that appears to be causative of disease. Measurement of FGF23 for hypophosphatemic patients is therefore useful for the diagnosis of FGF23-dependent hypophosphatemia.
| S-EPMC4377384 | biostudies-literature
Project description:X-linked hypophosphatemic rickets (XLH) is a dominantly inherited disorder characterized by renal phosphate wasting, aberrant vitamin D metabolism, and abnormal bone mineralization. XLH is caused by inactivating mutations in PHEX (phosphate-regulating gene with homologies to endopeptidases on the X chromosome). In this study, we sequenced the PHEX gene in subjects from 26 kindreds who were clinically diagnosed with XLH. Sequencing revealed 18 different mutations, of which thirteen have not been reported previously. In addition to deletions, splice site mutations, and missense and nonsense mutations, a rare point mutation in the 3'-untranslated region (3'-UTR) was identified as a novel cause of XLH. In summary, we identified a wide spectrum of mutations in the PHEX gene. Our data, in accord with those of others, indicate that there is no single predominant PHEX mutation responsible for XLH.
| S-EPMC2579265 | biostudies-literature
Project description:Context:Nephrocalcinosis (NC) and nephrolithiasis (NL) are described in hypophosphatemic rickets, but data regarding their prevalence rates and the presence of metabolic risk factors in X-linked hypophosphatemic rickets (XLH) are scarce. Objective:To determine the prevalence rates of NC and NL and their risk factors in patients with XLH with confirmed PHEX mutations. Methods:Renal ultrasonography (US) and CT were performed in 16 children and 23 adults. The images were evaluated by two blinded radiologists specializing in US and two specializing in CT. Confirmation of NC was determined with a positive result on both US and CT, whereas the diagnosis of NL was confirmed by CT alone. The presence of hypercalciuria, hypocitraturia, and hyperoxaluria was determined from 24-hour urinary samples from each patient. The glomerular filtration rate was estimated. Results:NC was identified in 15 patients (38.4%), and stratification by age group showed a higher prevalence of NC in children than in adults (56.2% vs 26.1%). CT identified NL in four adults (10.2%). Patients in the pediatric group required intensive use of phosphate, started treatment earlier, and presented greater phosphaturia than those in the adult group (P < 0.01). In addition to hyperphosphaturia, which was present in all patients with XLH, hypocitraturia was the most common metabolic factor (28.2%), whereas hypercalciuria occurred in two patients (5.1%). None had hyperoxaluria. Most patients had normal renal function. Conclusions:NC was more prevalent than NL. The main metabolic factor was hyperphosphaturia, and intensive phosphate treatment appears to be a worsening factor for kidney calcification.
| S-EPMC6497922 | biostudies-literature
Project description:X-linked hypophosphatemic rickets (HYP) is a dominant disorder characterized by renal phosphate wasting and abnormal vitamin D metabolism. PEX, the gene that is defective in HYP and is located on Xp22.1, is homologous to members of the neutral endopeptidase family. However, the complete coding sequence of the PEX cDNA, the structure of the PEX gene, and the role that PEX plays in phosphate transport remain unknown. We determined the genomic structure of the published PEX gene, which was found to be composed of 18 short exons, and demonstrated that the genomic organization of PEX shares homology to members of the family of neutral endopeptidases. Primer sets were designed from the intron sequence, to amplify each PEX exon from genomic DNA of HYP patients. Mutations in PEX were identified in 9/22 unrelated HYP patients, confirming that defects in PEX are responsible for HYP. The mutations detected included three nonsense mutations, a 1-bp deletion leading to a frameshift, a donor splice-site mutation, and missense mutations in four patients. Although the entire PEX gene has not been identified and some mutations may have been missed, the lack of detection of mutations in the remaining 13 patients, especially in 1 patient who has an apparently balanced, de novo 9;13 translocation, implies that there may be other loci involved in the generation of the HYP phenotype.
| S-EPMC1712471 | biostudies-other
Project description:ALPL encodes tissue-nonspecific alkaline phosphatase (TNAP), an enzyme expressed in bone, teeth, liver, and kidney. ALPL loss-of-function mutations cause hypophosphatasia (HPP), an inborn error-of-metabolism that produces skeletal and dental mineralization defects. Case reports describe widely varying dental phenotypes, making it unclear how HPP comparatively affects the three unique dental mineralized tissues: enamel, dentin, and cementum. We hypothesized that HPP affected all dental mineralized tissues and aimed to establish quantitative measurements of dental tissues in a subject with HPP. The female proband was diagnosed with HPP during childhood based on reduced alkaline phosphatase activity (ALP), mild rachitic skeletal effects, and premature primary tooth loss. The diagnosis was subsequently confirmed genetically by the presence of compound heterozygous ALPL mutations (exon 5: c.346G>A, p.A116T; exon 10: c.1077C>G, p.I359M). Dental defects in 8 prematurely exfoliated primary teeth were analyzed by high resolution micro-computed tomography (micro-CT) and histology. Similarities to the Alpl-/- mouse model of HPP were identified by additional analyses of murine dentoalveolar tissues. Primary teeth from the proband exhibited substantial remaining root structure compared to healthy control teeth. Enamel and dentin densities were not adversely affected in HPP vs. control teeth. However, analysis of discrete dentin regions revealed an approximate 10% reduction in the density of outer mantle dentin of HPP vs. control teeth. All 4 incisors and the molar lacked acellular cementum by micro-CT and histology, but surprisingly, 2 of 3 prematurely exfoliated canines exhibited apparently normal acellular cementum. Based on dentin findings in the proband's teeth, we examined dentoalveolar tissues in a mouse model of HPP, revealing that the delayed initiation of mineralization in the incisor mantle dentin was associated with a broader lack of circumpulpal dentin mineralization. This study describes a quantitative approach to measure effects of HPP on dental tissues. This approach has uncovered a previously unrecognized novel mantle dentin defect in HPP, as well as a surprising and variable cementum phenotype within the teeth from the same HPP subject.
| S-EPMC7769999 | biostudies-literature