AB020. What is advance in molecular diagnosis for 46,XY and 46,XX testicular disorder of sex development?

Background: The disorders of sex development (DSD) are defined by congenital conditions in which development of chromosomal, gonadal, or anatomical sex is atypical. It is estimated that genital anomalies occur in 1 in 4,500 births but 1:125 boys has hypospadias. There are three broad groups: 46,XX DSD, 46,XY DSD and sex chromosome aneuploidy DSD. Recently, exome sequencing followed by analysis with a list of all known human DSD-associated genes was used to investigate the underlying genetic etiology of 46,XY DSD patients who had not previously received a genetic diagnosis (E. C. Delot et al. ASHG meeting 2014). The authors identified a likely genetic diagnosis in more than a third of cases, including 22.5% with a pathogenic finding and an additional 12.5% with likely pathogenic findings. In addition, 15% had variants of uncertain clinical significance that may be reclassified as literature evolves.

Objective: To identify mutations in causative/candidate/susceptibility genes in patients with 46,XY DSD and 46,XX testicular DSD including AR, ATF3, BMP4, BMP7, BNC2, CTGF, CYP1A1, CYR61, DGKK, EGF, ESR1, ESR2, FGF8, FGFR2, GSTM1, GSTT1, HOXA4, HOXB6, HSD3B2, HSD17B3, MAMLD1, MID1, NR5A1 (alias SF1), SRD5A2, and WT1 genes. And to clarify the role of cryptic rearrangements in the development of 46,XY DSD in Vietnamese patients.

Patients and methods: A total of 61 cases with 46,XY were performed mutation analysis using PCR, next generation sequencing. Eight patients with 46,XX testicular DSD were analysed using whole genome and exome sequencing and 6 cases with 46,XY DSD associated with mental retardation and/or other congenital malformations were diagnosed molecular using CGH. Genomic DNA was extracted from lymphocytes of peripheral blood.

Results and conclusions: Two cases with primary adrenal insufficiency and 46,XY DSD from two unrelated families were identified novel homozygous mutation in HSD3B2 [c.481G>C (p.A161P)]. One case with simple hypospadias without adrenal insufficiency was identified mutation in HSD3B2 (p.A10T) gene. Six different causative mutations including 3 novel ones of AR gene were identified in 9 patients with androgen insensitivity syndrome [p.L701F (c.2103G>T); p.L705F (c.2113C>T); p. W752S (c. 2256 G>T); p.V747M (c.2239 G>A); p.V867M (c.2599 G>A) and p.Q28X (c.82C>T)]. Three causative mutations of SRD5A gene (coding for 5-alpha reductase) (p.S220L; p.R237G and p.R227Q) were identified in three patients from three unrelated families. Six cases with 46,XY DSD associated with mental retardation and/or other congenital malformation were identified cryptic rearrangements; 2 cases with 46,XX testicular DSD were identified duplication in SOX9. Advances in identification of molecular genetic causes of DSD will help confirmation of diagnosis, appropriate treatment and genetic counseling.

Keywords: Disorders of sex development (DSD); 46,XX testicular DSD; cryptic rearrangements