[Clinical and genetic analysis of a child with 46,XX male phenotype due to SOX3 gene duplication].

Abstract

Objective: To summarize the clinical and genetic characteristics of a child with 46,XX Ovotesticular disorder of sex development (46,XX OTDSD) due to copy number variation of SOX3 gene.

Methods: A 46,XX male patient presented at the Capital Center for Children's Health, Capital Medical University in November 2024 was selected as the study subject. Clinical data of the child was collected. Peripheral blood samples were taken from the child and his parents and subjected to trio whole-genome sequencing. Skewed X-chromosome inactivation was tested in the child and his mother. A literature review was carried out on 46,XX males associated with mutations of the SOX3 gene. This study was approved by the Medical Ethics Committee of the Hospital (Ethics No.: SHERLL2025056).

Results: The 10-year-old boy presented with hypospadias and cryptorchidism at birth. Chromosome analysis at one year and a half revealed a 46,XX karyotype. Gonadal biopsy showed testicular tissue, while ultrasound at the age of 10 detected ovotesticular tissue. Whole-genome sequencing identified a 660 kb duplication in the Xq27.1 region, which was derived from his mother. X-chromosome inactivation testing showed random inactivation in the child and mild non-random inactivation in the mother. Literature review has found 11 publications involving 15 patients (including our case), among whom 14 had a male social gender. They had primarily presented with hypospadias at birth but had no significant endocrine abnormalities. Most patients had experienced testicular failure after puberty. SOX3 related 46,XX males are mainly caused by de novo duplications, although a few maternal carriers had been discovered.

Conclusion: Duplication of the SOX3 gene probably underlay the pathogenesis is this 46,XX male. Individuals with 46,XX SRY negative male phenotypes should be routinely screened for SOX3 gene variants. Structural variations of the SOX3 gene can lead to complete or partial sex reversal in 46,XX individuals with minimal impact on intellectual and motor development, as well as other endocrine hormones.