The 46,XX testicular difference of sexual development (DSD) is where we find two X chromosomes in each cell (XX) (found in genetic females), but the person looks male in every other way.
People with 46,XX testicular DSD have a male phenotype. This is also known as 46,XX sex reversal, nonsyndromic 46,XX testicular DSD, XX male syndrome, or XX sex reversal.
This DSD occurs in about one in every 20,000 live births. 46,XX testicular DSD people have male genitals, with typically small or undescended testes. The urethra may open on the underside of the penis. Some children have variations in genitalia that don’t look typically male or female.
The majority of children with 46,XX testicular DSD are raised as males and are likely to have a male gender identity.
Why does 46,XX testicular DSD occur?
About 80 per cent of the time, the condition occurs due to the abnormal and random exchange of genetic material between chromosomes. This occurs for no clear reason as sperm forms in the affected person’s father.
The SRY gene is misplaced, but almost always on top of the X chromosome. If the foetus comes from a sperm cell that has an X chromosome belonging to the SRY gene, the child will develop as a male despite having no Y chromosome.
This version is called the SRY-positive 46,XX testicular DSD. The other 20 per cent do not have the SRY gene, which is known as SRY-negative 46,XX testicular DSD.
The cause in these cases is unknown, though other genes are known to be involved. Those with SRY-negative are more likely to have variations in the appearance of genitalia than those with the SRY-positive form.
Treatment and management of 46,XX DSD
Treatment and management will start at puberty with testosterone to trigger male sex characteristics to develop like facial hair and a deeper voice.
This treatment also prevents breast development. Adults tend to be shorter and are infertile.
References
- Arboleda VA, Sandberg DE, Vilain E. DSDs: genetics, underlying pathologies and psychosexual differentiation.Nat Rev Endocrinol. 2014;Oct;10(10):603-15. doi: 10.1038/nrendo.2014.130. Epub 2014 Aug 5.
- Vilain E. The genetics of ovotesticular disorders of sex development. Adv Exp Med Biol. 2011;707:105-6. doi: 10.1007/978-1-4419-8002-1_22.Wiersma R. The clinical spectrum and treatment of ovotesticular disorder of sexual development. Adv Exp Med Biol. 2011;707:101-3.
- Hughes IA, Houk C, Ahmed SF, Lee PA; Lawson Wilkins Pediatric Endocrine Society/European Society for Paediatric Endocrinology Consensus Group. Consensus statement on management of intersex disorders. J Pediatr Urol. 2006;2(3):148-62.
- Kim KR, Kwon Y, Joung JY, Kim KS, Ayla AG and Ro JY. True hermaphroditism and mixed gonadal dysgenesis in young children: A clinicopathologic study of 10 cases. Modern Pathology. 2002;15(10):1013-1.
- Hutcheson J, Snyder III HM. Ambiguous Genitalia and Intersexuality. Medscape.
- Medline Plus: A Service of the U.S. National Library of Medicine and the National Institutes of Health. Medical encyclopedia: Intersex.
- Ahmed F, Lucas-Herald A, McGowan R, Tobias E. Orphanet.
- NORD Rare Diseases, Eric Vilain, MD, PhD, Professor of Human Genetics, Pediatrics and Urology; Director, Center for Gender-Based Biology; Chief, Medical Genetics, Department of Pediatrics; David Geffen School of Medicine at UCLA
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