Differences of Sex Development: A Study of 420 Patients from a Single Tertiary Pediatric Endocrinology Center

<i>Background</i>: Differences of sex development (DSD) are a group of congenital conditions characterized by atypical development of genital structures. The diagnosis is complex and involves clinical, hormonal, and genetic evaluations. <i>Objective</i>: To describe the clinical profile, diagnosis, and management of patients with DSD, with particular attention to genetic diagnosis. <i>Study design</i>: Retrospective study from a tertiary care pediatric hospital in Italy. <i>Methods</i>: 420 patients with DSD referred to the Endocrine Unit of Bambino Gesù Children's Hospital in Rome, Italy, between 2016 and 2023 were included. <i>Results</i>: 75 patients had a 46,XY karyotype, 135 had a 46,XX karyotype, and 210 had chromosomal mosaicism. In our group of pediatric DSD patients, 21/420 patients were born from pregnancies induced with assisted reproduction techniques (ICSI/FIVET). Of these 21 patients, 5 had sex chromosome mosaicism. Using next-generation sequencing (NGS), we identified three new genetic variants: one in the <i>AR</i> gene, one in the <i>NR5A1</i> gene, and one in the <i>SRY</i> gene. The use of NGS significantly improved the diagnostic yield, and a definitive diagnosis was reached in 84.76% of the entire cohort. <i>Conclusions:</i> This study highlights the challenges in the management of patients with DSD from early recognition to treatment and follow-up. A multidisciplinary approach is essential for a comprehensive evaluation of these conditions and to understand the role and clinical significance of the genetic variants.