Cytogenomic Investigation of Individuals with Ovotesticular Difference of Sex Development.

INTRODUCTION: Ovotesticular Difference of Sex Development (OT-DSD) may result from chimerism, mosaicism, structural or sequence variants. However, even after investigating all known causes, many individuals still lack an established etiology. This study aimed to perform cytogenomic investigation of individuals with OT-DSD. METHODS: The sample consisted of 15 individuals with OT-DSD. Methods included G-banding karyotype, Chromosomal Microarray Analysis (CMA), Optical Genome Mapping (OGM), and Whole-Genome Sequencing (WGS). RESULTS: G-banding karyotype revealed chimerism in two individuals, mosaicism in one, and 47,XXY karyotype in another. One individual had a pericentric inversion at the X chromosome, with breakpoints mapped close to SOX3. Ten individuals had a normal karyotype, eight 46,XX, and two 46,XY. CMA, performed in 11, identified a duplication including the SOX3 gene in one 46,XX individual, and two duplications in a 46,XY individual, with breakpoints mapped by WGS, suggesting a complex rearrangement that could affect VAMP7 expression. OGM was performed in two individuals and WGS in nine individuals, which did not reveal additional relevant structural variants (SVs). CONCLUSION: Cytogenomic methods identified causative alterations in 5/15 (33.3%) individuals, underscoring the need to combine complementary approaches to detect and characterize SVs. In the remaining cases, the etiology was undetermined, emphasizing the need for further molecular investigations.