SRY translocation (46,XX testicular DSD)
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A phenotypically male adult presents with infertility and small testes. Karyotype reveals 46,XX. FISH shows the SRY gene translocated to one X chromosome. The patient has male external genitalia, no uterus, and azoospermia.
Translocation of SRY (sex-determining region Y) from Yp to Xp
- Most commonly occurs via aberrant X-Y recombination during paternal meiosis
- SRY is sufficient to initiate male sex determination (testis formation)
- Results in a 46,XX individual with male phenotype
- ~10% of 46,XX testicular DSD cases are SRY-negative (other genes involved)
- Male external genitalia (usually normal)
- Small testes
- Azoospermia and infertility (no spermatogenesis; requires AZF region genes on Yq)
- Gynecomastia (variable)
- Short stature (no Y chromosome growth genes)
- Normal to mildly reduced testosterone
- No uterus or fallopian tubes (AMH present from Sertoli cells)
- Karyotype: 46,XX
- FISH or CMA: SRY signal on X chromosome
- Hormone panel: elevated FSH/LH, low-normal testosterone
- Testosterone replacement for hypogonadism (supports virilization, libido, and bone health)
- Counsel that azoospermia causes infertility; the absent Yq AZF region precludes spermatogenesis, so sperm retrieval is not successful and donor sperm or adoption are the options for building a family
- Address gynecomastia if present (surgical correction); psychological support
- Genetic counseling: usually de novo from aberrant paternal X-Y recombination; low recurrence risk
"SRY = Sex Region on Y": SRY is the master switch for male development. When it translocates to X, the result is a 46,XX male.
46,XX male vs Klinefelter (47,XXY): Both present with small testes and infertility, but SRY translocation has a normal 46,XX karyotype with SRY on FISH. Klinefelter has 47,XXY and is typically taller.