6864 Genetic Profile And Identification Of A Novel Mutation In PHEX In X-Linked Hypophosphatemia (XLH) Patients At A Brazilian Research Center: Insights And Implications

Abstract Disclosure: M. Monseff Rodrigues da silva: None. I.M. de Araújo: None. F.J. de Paula: None. Background: X-Linked Hypophosphatemia (XLH) is a rare genetic disorder characterized by low phosphate levels in the blood, primarily caused by mutations in the PHEX gene, leading to bone skeletal deformities and reduced quality of life. XLH genetics is extensively studied with over 500 pathogenic mutations in the PHEXgene having been identified. Common mutations include missense, nonsense, and splicing, accounting for approximately 50% of cases. However, genotype-phenotype correlations remain unclear. Methods: We conducted a cross-sectional study using a convenience sample selected from the osteometabolism an outpatient clinic in Brazil. Genetic analysis was performed using next-generation sequencing (NGS; Ilumina) in collaboration with Mendelics Laboratory. Results: In our study, 9 out of 10 patients showed previously known and reported mutations, with 60% exhibiting common mutation types. The mutations occur in different codons; however, the most prevalent consequence was the substitution of glycine (G) with adenine (A), present in 40% of the patients. One patient, however, showed a unique missense mutation in PHEX gene (arginine to glutamate at codon 266), which leads to a premature stop codon, a mutation absent in over 183,000 X chromosomes from XLH individuals. Even though this mutation was novel, no significant diferences in the phenotype of this patient were seen in comparision with the rest of the cohort. Discussion: The findings of our study underscore the genetic heterogeneity characteristic of XLH, as evidenced by the fact that 90% of our patient cohort exhibited mutations previously identified in the literature, with a significant 60% showing common mutation types. This highlights the recurring genetic patterns in XLH, which can be instrumental for diagnostic and - perhaps in the future - therapeutic strategies. Particularly notable is the predominant mutation involving the substitution of glycine with adenine, found in 40% of our patients, underscoring its potential role as a key mutation in the pathogenesis of XLH. Furthermore, the discovery of a novel missense mutation in one patient, resulting in a premature stop codon, enriches the mutation spectrum of XLH and suggests a deeper complexity in the genetic landscape of the disease. This mutation, not previously documented in the extensive database of over 183,000 X chromosomes from XLH individuals, opens new avenues for research into the disease's molecular mechanisms and potential genotype-phenotype correlations. Conclusion: This study underlines the genetic diversity within XLH, emphasizing the need for comprehensive genetic analysis to understand the full spectrum of the disease. More studies are yet necessary to elucidate if there is a genotype-phenotype correlation. Presentation: 6/1/2024