Clinical and molecular characterization of DSD patients: Impact of Next Generation Sequencing in diagnosis

317 p.Disorders of sex development (DSD) encompass a high heterogeneous range of conditionsin which the optimal clinical management of the individuals comprise clinical description, biochemicaltesting and genetic analysis. With the arrival of next-generation sequencing (NGS) new genes andpathways have been implicated in the pathogenesis of the disease. However, only 50% of the 46,XY DSDpatients will receive a definitive diagnosis. The aim of this work is the clinical and molecularcharacterization of a DSD cohort. Patients and methods: Blood samples or DNA from a total of 125independent patients with a DSD referred from several Spanish centres and one Swiss hospital werestudied. Clinical characterization was done after examination of the data sheet provided by the clinicians.The molecular study was performed either by single-gene testing or NGS using a targeted gene panel of48 DSD-related genes. Parents were also analysed when possible. Genetic variants were analysed usingin silico prediction programmes and were classified according to its potential pathogenicity. Furtherfunctional studies of the genetic changes identified in three genes were also performed. Results: Overall,we made a genetic diagnosis in 4.4% of the individuals. In 46,XY DSD, the diagnostic rate increased upto 46.5% while in 46.XX DSD it was 29.2%. Novel changes classified as pathogenic or likely pathogenicwere mostly located in the NR5A1 and LHCGR genes. Functional impact of variants in NR5A1 andLHCGR showed a significant reduced transactivation activity while the variant of unknown significancein GATA4 showed similar activity compared to wild type. Conclusions: The heterogeneous phenotypesencompassed in this condition difficult the clinical diagnosis and highlight the need of a genetic study.The molecular analysis of DSD-related genes identified a causative genetic variant in the 40.2% of thepatients analysed in this cohort. Targeted gene sequencing panel is useful for the detection of singlenucleotidevariants, however further improvements are needed to detect copy number variations.Functional studies are a valuable tool to confirm the effect of a variant in the pathogenesis of the disease