22q13 Duplication in Newborn With Dysmorphic Features: The Role of SOX10 in Disorders of Sex Development

Background: The 46,XX testicular disorder of sex development (DSD), also known as 46,XX male reversal, is a rare form of DSD and clinical phenotype shows complete sex reversal from female to male. The sex-determining region Y (SRY) gene can be identified in most 46,XX testicular DSD patients; however, approximately 20% are SRY-negative. Here we present a 2 week old with discrepant prenatal karyotype and infant phenotype. Case: This 2-week-old had dysmorphic features (bitemporal narrowing, broad and flat nasal bridge, bilateral epicanthal folds) and multiple congenital anomalies; IUGR, hypertelorism, cleft lip and palate, ASD, small kidneys, sacral dimple. Physical exam revealed palpable inguinal masses and microphallus without hypospadias. Postnatal karyotype showed a 46,XX chromosome complement with duplication of 22q13-qter. He was negative for SRY gene by FISH. Microarray analysis confirmed the duplication encompassing the SOX10 gene. Lab evaluation showed LH 10.81 mIU/ml, FSH 3.21 mIU/ml and total testosterone 241 ng/dl. These values are consistent with activation of the hypothalamic–pituitary–gonadal axis during the neonatal period in males. Conclusion: Our case along with previous cases supports the existence of a gene on chromosome 22q that can trigger testis determination in the absence of SRY. Potential mechanisms responsible for ovotesticular disorder in the XX (SRY−) individual could involve activation of testis specifying genes in the absence of SRY and/or inadequate expression of pro-ovary/anti-testis genes such as SOX 8 and SOX9. SOX10, a gene closely related to SOX9 and SOX8, and its overexpression has been suggested as a candidate for 46,XX DSD. Over-expression of SOX10 in mice resulted in the XX DSD. The spectrum of sex reversal phenotypes and gonadal asymmetry seen in the Sox10 transgenic mice closely mirrors the range of gonadal and reproductive tract anomalies seen in cases of partial duplication of human chromosome 22q13. Although SRY-negative 46,XX testicular DSD is a rare condition, an effort to make an accurate diagnosis is important for the provision of proper genetic counseling and for guiding patients in their long-term management.