Phenotypes linked to duplication upstream of SOX9: New insights into presentation and diagnosis.

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.

Design And Setting: We retrospectively analyzed data of 46,XX/SRY-negative individuals with SOX9 upstream duplications.

Methods: 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 twelve 46,XX individuals with heterozygous duplications upstream of SOX9, ranging from 107-941 kb. Ages at diagnosis ranged from 0.1 to 55 years. Seven (58%) had testicular/ovotesticular DSD, while five (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 the 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.