ESPE Abstracts

Disorders/differences in sex development (DSD) are defined as congenital conditions in which development of chromosomal, gonadal or anatomical sex is atypical. 46,XY DSD include defects in androgen synthesis or action or complete (CGD)/partial (PGD) gonadal dysgenesis. The aim of this study was to characterize the molecular genetic diagnosis of individuals with 46,XY DSD followed at Garrahan Pediatric Hospital.

Medical records of 140 patients (P) followed at the Endocrinology Department because of 46, XY DSD were reviewed. DNA samples were obtained in 84/140. Subjects were divided into 3 groups based on clinical characteristics, hormonal measurements, gonad histology and ultrasound/laparoscopic findings:defects in androgen synthesis (group 1, G1 n=8) or action (group 2, G2 n=34) and CGD/PGD (group 3, G3 n=40). First, candidate gene sequencing was performed:in G1 StAR, CYP17A1,HSD3B2,POR or SRD5A2; in G2 AR and in G3 SRY, NR5A1 and/or WT1. Copy number variations (CNVs) of SRY, SOX9, NR0B1, NR5A1 and WNT4 were assessed by MLPA in G3, both in DNA from peripheral blood leukocytes and, when available, gonadal tissue. In this group, a panel of 35 genes known to cause XY DSD or known to play a role in gonadal differentiation and genitourinary tract development was designed for next generation sequencing (NGS). Moreover, whole exome sequencing (WES) was conducted in the remaining undiagnosed individuals. Every clinically significant variant was confirmed by Sanger sequencing in proband and parents to elucidate inheritance pattern.

In G1, deleterious gene mutations were detected in StAR (n:1), CYP17A1 (n:1), HSD3B2 (n:2), POR (n:2) and SRD5A2 (n:2). In G2,AR mutations were found in 22 subjects of 14 families (F). In G3, mutations were found in SRY (2 siblings), NR5A1 (n:7 F) and WT1 (n:9). No CNVs were found by MLPA in peripheral blood or gonad DNA. The designed gene panel allowed the diagnosis of 4 P in whom mutations in ZFPM2 gene were found. WES analysis revealed mutations in DHX37 gene in 2 P.

In this cohort, excluding enzymatic defects, molecular characterization was reached in approximately 43% (36/84). Diagnosis in 46,XY DSD can be challenging due to overlapping clinical characteristics or poor genotype/phenotype correlation. Thus, candidate gene sequencing strategy might not be adequate in all cases. NGS can be a better approach to reach an etiologic diagnosis reducing time and medical interventions. However, other etiologies should be considered: non coding genomic regions, oligo/multigenic inheritance, epigenetic pathways or environmental factors.