Phenotypes Linked to Duplication Upstream of SOX9: New Insights Into Presentation and Diagnosis

Abstract Context Duplications occurring upstream of the SOX9 gene have been identified in a limited subset of patients with 46,XX testicular/ovotesticular differences/disorders of sex development (DSD). However, comprehensive understanding regarding their clinical presentation and diagnosis is limited. Objective To gain further insight into the diagnosis of a large cohort of 46,XX individuals with duplications upstream of SOX9. Methods We retrospectively analyzed data of 46,XX/SRY-negative individuals with SOX9 upstream duplications. Clinical data were recorded, and genetic etiologies were investigated using karyotyping, fluorescence in situ hybridization (FISH) for SRY analysis, microarray analysis, multiplex ligation-dependent probe amplification (MLPA) and next-generation sequencing panels including whole genome sequencing. Results We analyzed 12 individuals with 46,XX karyotype who had heterozygous duplications upstream of SOX9, ranging from 107 to 941 kb. Ages at diagnosis ranged from 0.1 to 55 years. Seven (58%) had testicular/ovotesticular DSD, while 5 (41%) were asymptomatic carriers detected through family screening. There was no significant correlation between duplication size and genital/gonadal phenotype. The duplication was inherited from the father (n = 3) or an asymptomatic mother (n = 2). In one family, a duplication missed by the 300K microarray was detected by MLPA and confirmed with 750K microarray. Conclusion 46,XX individuals with SOX9 upstream duplications may exhibit no symptoms, but thorough family screening is crucial due to the potential inheritance and testicular/ovotesticular DSD risk in subsequent generations. We emphasize the effectiveness of high-resolution microarray analysis (>500K) as the primary diagnostic tool for 46,XX/SRY-negative testicular/ovotesticular DSD individuals, enabling thorough genome-wide assessment of copy number variations and detecting small alterations.