THU185 Molecular Etiologic Spectrum Of Patients With 46,XY And 46,XX Disorders Of Sex Development

Disclosure: J. Kim: None. S. Park: None. S. Hwang: None. J. Yoon: None. G. Kim: None. H. Yoo: None. J. Choi: None. Background: Disorders of sexual development (DSDs) is a group of congenital conditions associated with discordant development of chromosomal, gonadal, and anatomical sex. Sex development is a complex process with a precise synergistic temporal-spatial transcriptional regulation of multiple genes. Advances in next-generation sequencing (NGS) techniques have achieved genetic diagnosis for up to 40 % of 46,XY DSDs. This study investigated the etiological distribution of DSDs identified by NGS. Methods: This study included 70 patients with DSDs (56 patients with 46,XY DSD and 14 patients with 46,XX DSD). Molecular genetic analysis was performed using targeted gene panel sequencing (n = 43) and whole-exome sequencing (WES, n = 26), including 25 patients for the first-line test and one without sequence variants by targeted gene panel sequencing. Whole-genome sequencing (WGS) was performed on 7 patients, including two patients for the first-line test and five patients without sequence variants by targeted gene panel sequencing or WES. Results: Patients with DSDs presented in infancy with ambiguous genitalia and at older children with aberrant pubertal development or discordance between karyotype and external genitalia. Twenty-four of 56 patients (42.9%) with 46,XY DSD were reared female, and 5 of 14 patients (35.7%) with 46,XX DSD were raised as a male. Pathogenic or likely pathogenic variants were identified in 21 of 56 patients with 46,XY DSD (37.5%); however, no rare sequence variants were found in patients with 46,XX DSD. The AR variants were the most common (8/70, 11.4%), followed by CYP17A1 (4/70, 5.7%), SRD5A2 (4/70, 5.7%), NR5A1 (2/70, 2.8%), GATA4 (1/70, 1.4%), MYRF (1/70, 1.4%), and deletion of DMRT1/2 (1/70, 1.4%). Mutation-positive patients with 46, XY DSD were assigned as female more frequently than mutation-negative patients (19/21 vs. 6/35, P-value <0.001). The lower diagnostic yield was observed in patients with a less severe phenotype, such as hypospadias or micropenis. Conclusions: This study demonstrated that genetic etiologies could be identified in 37.5% of patients with 46,XY DSD, whereas there were no genetic variants in patients with 46,XX DSD. Patients with a more severe phenotype were more likely to have a conclusive genetic diagnosis. NGS is a helpful technique to improve diagnostic efficiency in patients with DSD because of phenotypic and genetic heterogeneity. Presentation: Thursday, June 15, 2023