UNASSIGNED: The aim of this study was to evaluate the effectiveness of burosumab therapy in children with X-Linked Hypophosphatemia (XLH).
UNASSIGNED: We systematically reviewed literature from PubMed, Web of Science, The Cochrane Library, and Embase up until January 2024, using EndNote Web for study organization. The Newcastle-Ottawa scale guided quality assessment, while Revman software was used for data analysis and visualization. Study selection, quality evaluation, and data aggregation were independently performed by three researchers.
UNASSIGNED: The meta-analysis encompassed ten studies, including eight cohort studies that examined burosumab\'s impact pre- and post-administration, and two randomized controlled trials comparing burosumab to standard therapy. The evidence from this review suggests burosumab\'s superiority in managing XLH in pediatric populations, particularly in improving key biochemical markers including 1,25-dihydroxyvitamin D (1,25-(OH)2D), phosphorus, and alkaline phosphatase (ALP), alongside improvements in the renal tubular maximum reabsorption rate of phosphate to glomerular filtration rate (TmP/GFR), and significant skeletal improvements as indicated by the rickets severity score (RSS) and the 6-minute walk test (6MWT). However, the long-term safety and effects, including height and quality of life (QOL) data, remains to be elucidated.
UNASSIGNED: Burosumab has shown significant therapeutic effectiveness in treating children with XLH, highlighting its potential as a key treatment option.

BACKGROUND: X-linked hypophosphatemia (XLH) is the most common inherited form of rickets. The presence of sequence variations in the phosphate regulating endopeptidase homolog X-linked (PHEX) gene is associated with increased production of fibroblast growth factor 23 (FGF23). This results in renal phosphate wasting and impaired skeletal mineralization. Spontaneous dental abscesses, caused by endodontic infections resulting from hypomineralization of dentin, are a known dental complication of XLH. There is no objective method to evaluate the severity of dentin dysplasia. The purpose of this study was to develop a quantitative method to evaluate dentin dysplasia using orthopantomography that would allow the values in patients with XLH to be compared with the values in healthy participants of the same age.
METHODS: The severity of dentin dysplasia was analyzed by measuring the pulp cavity area of the tooth using orthopantomographic images. The teeth analyzed were mandibular second primary molars and mandibular first permanent molars with complete root formation. Teeth with dental caries, restorations, or root resorption were excluded.
RESULTS: This retrospective observational study included a total of 200 images of healthy participants (aged 2-15 years) divided into five age groups and 42 images of 17 patients with XLH. There was a significant tendency for the pulp cavity area to decrease with increasing age in primary and permanent teeth. The pulp chambers of patients with XLH were larger than those of healthy participants in primary and permanent teeth.
CONCLUSIONS: We have established a method of using orthopantomography for quantitative assessment of dentin dysplasia in XLH from the primary dentition to the permanent dentition. Evaluating the severity of dentin hypomineralization by this method is useful in the diagnosis of the dental manifestations of XLH. Early diagnosis of XLH enables oral management and leads to prevention of dental abscesses.

BACKGROUND: Hereditary vitamin D resistant rickets (HVDRR) is a rare autosomal recessive disorder marked by end-organ resistance of 1,25-dihydroxyvitamin D secondary to various mutations in the vitamin D receptor gene. The currently accepted treatment modality involves bypassing the affected receptors in the gut with high-dose intravenous calcium. In a few limited case reports, cinacalcet, a calcimimetic, has been used as an adjunctive therapy.
METHODS: Retrospective chart reviews were conducted to collect the clinical and biochemical data of 8 patients with HVDRR from 5 Saudi families. Four patients received only high-dose calcium, while the remaining 4 received adjuvant cinacalcet. Serum chemistry and PTH levels were measured before and during cinacalcet treatment. Gene sequencing was performed to identify the disease-causing mutation.
RESULTS: All 8 patients exhibited alopecia and secondary hyperparathyroidism. Other clinical and biochemical features of rickets were present to varying degrees. Genetic analysis revealed 3 distinct mutations: a ligand-binding domain mutation in 3 unrelated patients, a ligand-binding domain mutation in 2 sisters, and a missense DNA-binding domain mutation in 3 brothers. While the overall response to therapy was variable, none of the 4 patients who received adjunctive cinacalcet developed hypocalcaemia, and there was some initial promise in improving serum PTH levels.
CONCLUSIONS: This series provides new insight into the clinical and biochemical characteristics as well as treatment responses in Saudi children with HVDRR. The findings suggest that cinacalcet is a safe and potentially valuable adjuvant in this understudied population; however, further research is required to verify these results.

X-linked hypophosphatemia (XLH) is a rare inherited disorder of renal phosphate wasting with a highly variable phenotype caused by loss-of-function variants in the PHEX gene. The diagnosis of individuals with mild phenotypes can be challenging and often delayed. Here, we describe a three-generation family with a very mild clinical presentation of XLH. The diagnosis was unexpectedly found in a 39-year-old woman who was referred for genetic testing due to an unclear childhood diagnosis of a tubulopathy. Genetic testing performed by next-generation sequencing using a kidney disease gene panel identified a novel non-canonical splice site variant in the PHEX gene. Segregation analysis detected that the consultand\'s father, who presented with hypophosphatemia and decreased tubular phosphate reabsorption, and the consultand\'s son also carried this variant. RNA studies demonstrated that the non-canonical splice site variant partially altered the splicing of the PHEX gene, as both wild-type and aberrant splicing transcripts were detected in the two male members with only one copy of the PHEX gene. In conclusion, this case contributes to the understanding of the relationship between splicing variants and the variable expressivity of XLH disease. The mild phenotype of this family can be explained by the coexistence of PHEX transcripts with aberrant and wild-type splicing.

UNASSIGNED: Hereditary Vitamin D-dependent rickets type II (HVDDR-type II) is a rare autosomal recessive disorder caused by molecular variation in the gene encoding the vitamin D receptor (VDR). This study aims to evaluate phenotype and genotype characteristics and long-term follow-up of the largest group of patients with (HVDDR-type II) in Saudi Arabia.
UNASSIGNED: We conducted a retrospective chart review to collect the clinical, biochemical, and genetic data for all HVDDR-type II patients currently receiving treatment at King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia.
UNASSIGNED: A total of 42 patients, 57.1% female, and 42.9% male were included in the study. Seven patients were treated with high doses of oral calcium, while 35 patients were treated with IV calcium infusion. The median age at presentation was 15.5 months. Alopecia was found in 97.6%, 21.4% presented with bowing legs, 14.3% with delayed walking, 9.5% with seizure, and 2.4% presented with respiratory failure, while a family history of the disease was positive in 71.4% of total patients. Molecular genetic testing of the VDR gene in our cohort identified six different gene variants c.885 C>A (p.Tyr295Ter), c.88 C>T (p.Arg30Ter), c.1036G>A (p.Val346Met), c.820C>T (p.Arg274Cys), c.803 T>C (p.Ile268Thr), and c.2T>G (p.Met1?).
UNASSIGNED: We are describing the largest cohort of patients with HVDDR-type II, their clinical biochemical findings, and the most prevalent genetic variants in our population.

X-linked hypophosphatemia (XLH) is caused by mutations in PHEX, leading to rickets and osteomalacia. Adults affected with XLH develop a mineralization of the bone-tendon attachment site (enthesis), called enthesopathy, which causes significant pain and impaired movement. Entheses in mice with XLH (Hyp) have enhanced bone morphogenetic protein (BMP) and Indian hedgehog (IHH) signaling. Treatment of Hyp mice with the BMP signaling blocker palovarotene attenuated BMP/IHH signaling in Hyp entheses, thus indicating that BMP signaling plays a pathogenic role in enthesopathy development and that IHH signaling is activated by BMP signaling in entheses. It was previously shown that mRNA expression of growth/differentiation factor 5 (Gdf5) is enhanced in Hyp entheses at P14. Thus, to determine a role for GDF5 in enthesopathy development, Gdf5 was deleted globally in Hyp mice and conditionally in Scx + cells of Hyp mice. In both murine models, BMP/IHH signaling was similarly decreased in Hyp entheses, leading to decreased enthesopathy. BMP/IHH signaling remained unaffected in WT entheses with decreased Gdf5 expression. Moreover, deletion of Gdf5 in Hyp entheses starting at P30, after enthesopathy has developed, partially reversed enthesopathy. Taken together, these results demonstrate that while GDF5 is not essential for modulating BMP/IHH signaling in WT entheses, inappropriate GDF5 activity in Scx + cells contributes to XLH enthesopathy development. As such, inhibition of GDF5 signaling may be beneficial for the treatment of XLH enthesopathy.
X-linked hypophosphatemia (XLH) is a rare bone disorder that leads to short stature and poorly mineralized bones. As adults, patients with XLH often develop a mineralization of the bone-tendon attachment site, called enthesopathy, which results in significant pain. We previously showed that Achilles bone-tendon attachment sites (entheses) in mice with XLH (Hyp) have an enthesopathy characterized by increased bone morphogenetic protein (BMP) signaling. In the current studies, we show that treating Hyp mice with the BMP signaling inhibitor palovarotene prevents enthesopathy, demonstrating that the increased BMP signaling in Hyp entheses leads to enthesopathy development. We also reported that gene expression of Gdf5, which activates BMP signaling, is enhanced in Hyp entheses. Therefore, to determine if the enhanced Gdf5 expression leads to the increased BMP signaling seen Hyp entheses, Gdf5 was deleted from Hyp mice and also deleted specifically in the entheses of Hyp mice. In both mouse models, enthesopathy development was attenuated, demonstrating that the increased Gdf5 expression in Hyp entheses plays a role in enthesopathy development. These data indicate that blocking GDF5 and BMP signaling may prevent enthesopathy in patients with XLH.

UNASSIGNED: X-linked hypophosphatemia (XLH) is caused by an inactivating mutation in the phosphate-regulating endopeptidase X-linked (PHEX) gene whose defective product fails to control phosphatonin fibroblast growth factor 23 (FGF23) serum levels. Although elevated FGF23 levels have been linked with detrimental cardiac effects, the cardiologic outcomes in XLH patients have been subject to debate. Our study aimed to evaluate the prevalence and severity of cardiovascular morbidity in pediatric XLH patients before, during, and after a 2-year treatment period with burosumab, a recombinant anti-FGF23 antibody.
UNASSIGNED: This prospective observational study was conducted in a tertiary medical center, and included 13 individuals with XLH (age range 0.6-16.2 years) who received burosumab every 2 weeks. Clinical assessment at treatment initiation and after .5, 1, and 2 years of uninterrupted treatment included anthropometric measurements and cardiologic evaluations (blood pressure [BP], electrocardiogram, conventional echocardiography, and myocardial strain imaging).
UNASSIGNED: The linear growth of all patients improved significantly (mean height z-score: from -1.70 ± 0.80 to -0.96 ± 1.08, P=0.03). Other favorable effects were decline in overweight/obesity rates (from 46.2% to 23.1%) and decreased rates of elevated BP (systolic BP from 38.5% to 15.4%; diastolic BP from 38.5% to 23.1%). Electrocardiograms revealed no significant abnormality throughout the study period. Cardiac dimensions and myocardial strain parameters were within the normative range for age at baseline and remained unchanged during the study period.
UNASSIGNED: Cardiologic evaluations provided reassurance that 2 years of burosumab therapy did not cause cardiac morbidity. The beneficial effect of this treatment was a reduction in cardiovascular risk factors, as evidenced by the lower prevalence of both overweight/obesity and elevated BP.

Burosumab, a monoclonal antibody directed against the fibroblast growth factor 23 (FGF23), has been approved for the treatment of X-linked hypophosphatemia (XLH). We conducted a systematic review to compare the efficacy and safety of burosumab versus conventional therapy (phosphorus and calcitriol) on XLH treatment. After a comprehensive literature search on MEDLINE/PubMed and Embase, we found nine studies for inclusion in the analysis. Risk of bias was assessed, and a random-effects model was used to determine the effect size. Clinical, biochemical, and radiological parameters of disease severity before and after treatment were analyzed and expressed in standardized mean difference (SMD). Burosumab resulted in normalization of phosphate homeostasis with an increase in renal tubular phosphate reabsorption and significant resolution of skeletal lesions (change in Thacher\'s total rickets severity score SMD: -1.46, 95% confidence interval [CI]: -1.76 to -1.17, p < 0.001, improvement in deformities, and decline in serum alkaline phosphatase levels [SMD: 130.68, 95% CI: 125.26-136.1, p < 0.001)]. Conventional therapy led to similar improvements in all these parameters but to a lower degree. In adults, burosumab normalized phosphorus levels (SMD: 1.23, 95% CI: 0.98-1.47, p < 0.001) with resultant clinical improvement. Burosumab treatment was well tolerated, with only mild treatment-related adverse effects. The present review indicates a potential role for burosumab in improving rickets, deformities, and growth in children with XLH. Given its superior efficacy and safety profile, burosumab could be an effective therapeutic option in children. We suggest further studies comparing burosumab versus conventional therapy in children and adults with XLH.

OBJECTIVE: X-linked hypophosphatemia (XLH) is a rare multi-systemic disease characterized by low plasma phosphate levels. The aim of this study was to investigate the annual XLH prevalence and internally evaluate predictive algorithms\' application performance for the early diagnosis of XLH.
METHODS: The PediaNet database, containing data on more than 400,000 children aged up to 14 years, was used to identify a cohort of XLH patients, which were matched with up to 10 controls by date of birth and gender. The annual prevalence of XLH cases per 100,000 patients registered in PediaNet database was estimated. To identify possible predictors associated with XLH diagnosis, a logistic regression model and two machine learning algorithms were applied. Predictive analyses were separately carried out including patients with at least 1 or 2 years of database history in PediaNet.
RESULTS: Among 431,021 patients registered in the PediaNet database between 2007-2020, a total of 12 cases were identified with a mean annual prevalence of 1.78 cases per 100,000 patients registered in PediaNet database. Overall, 8 cases and 60 matched controls were included in the analysis. The random forest algorithm achieved the highest area under the receiver operating characteristic curve (AUC) value both in the one-year prior ID (AUC = 0.99, 95% CI = 0.99-1.00) and the two-year prior ID (AUC = 1.00, 95% CI = 1.00-1.00) analysis. Overall, the XLH predictors selected by the three predictive methods were: the number of vitamin D prescriptions, the number of recorded diagnoses of acute respiratory infections, the number of prescriptions of antihistamine for systemic use, the number of prescriptions of X-ray of the lower limbs and pelvis and the number of allergology visits.
CONCLUSIONS: Findings showed that data-driven machine learning models may play a prominent role for the prediction of the diagnosis of rare diseases such as XLH.

X-linked hypophosphatemia (XLH) is a rare genetic disorder that increases fibroblast growth factor 23 (FGF23). XLH patients have an elevated risk of early-onset hypertension. The precise factors contributing to hypertension in XLH patients have yet to be identified. A multicenter cross-sectional study of adult patients diagnosed with XLH. Metabolomic analysis was performed using ultra-performance liquid chromatography (UPLC) coupled to a high-resolution mass spectrometer. Twenty subjects were included, of which nine (45%) had hypertension. The median age was 44 years. Out of the total, seven (35%) subjects had a family history of hypertension. No statistically significant differences were found between both groups for nephrocalcinosis or hyperparathyroidism. Those with hypertension exhibited significantly higher levels of creatinine (1.08 ± 0.31 mg/dL vs. 0.78 ± 0.19 mg/dL; p = 0.01) and LDL-C (133.33 ± 21.92 mg/dL vs. 107.27 ± 20.12 mg/dL, p = 0.01). A total of 106 metabolites were identified. Acetylcarnitine (p = 0.03), pyruvate p = (0.04), ethanolamine (p = 0.03), and butyric acid (p = 0.001) were significantly different between both groups. This study is the first to examine the metabolomics of hypertension in patients with XLH. We have identified significant changes in specific metabolites that shed new light on the potential mechanisms of hypertension in XLH patients. These findings could lead to new studies identifying associated biomarkers and developing new diagnostic approaches for XLH patients.