A Rare Differences of Sex Development: Male Sex Reversal Syndrome (NonSyndromic 46, XX with Negative Sex-Determining Region of Y Chromosome Gene)

46, XX testicular differences of sex development (DSD) is a rare cause of DSD presenting as a phenotypical male with chromosomal sex of 46, XX. Sex-determining region of the Y chromosome (SRY)-positive 46, XX DSDs have a well-characterized pathogenetic mechanism, whereas in SRY-negative 46, XX DSDs, the pathogenesis is not clearly delineated. Herein, we present a case of a 3½-year-old child who presented with ambiguous genitalia and bilateral palpable gonads. On the basis of a karyotype and fluorescent in situ hybridization, we arrived at a diagnosis of SRY-negative 46, XX testicular DSD. Basal serum estradiol and human menopausal gonadotrophin stimulated estradiol levels and inhibin A blood levels were against the presence of any ovarian tissue. Imaging of the gonads showed bilateral normal-looking testis. A clinical exome sequencing revealed a heterozygous missense variant NR5A1:c275G>A (p. Arg92gln) located at exon 4 in the affected child. Protein structure analysis was further performed, and the variant was found to be highly conserved. Sanger's sequencing showed that the mother was heterozygous for the variant detected in the child. This case highlights the rarity of SRY-negative 46, XX testicular DSD with a unique variant. Largely under characterized, this group of DSDs needs to be reported and analyzed to add to the spectrum of presentation and genetic characteristics. Our case is expected to add to the database, knowledge, and approach to cases of 46, XX testicular DSD.