Mutation in the SRY gene (the sex-determining region of the Y chromosome) is noted in 10–15% of the cases, whereas the rest are unexplained.
Despite the presence of the Y chromosome, there is underexpression of the anti-mullerian hormone (AMH) and the androgenic hormones due to the dysgenetic gonads, leading to female type of internal and external genitalia. The hormonal parameters are indicative of hypergonadotropism (increased LH and FSH) with normal or low testosterone levels.
People with Swyer syndrome have typical female external genitalia. The uterus and fallopian tubes are normally formed, but the gonads (ovaries or testes) are not functional; affected individuals have undeveloped clumps of tissue called streak gonads. Due to the lack of development of the gonads, Swyer syndrome is also called 46, XY complete gonadal dysgenesis. The residual gonadal tissue often becomes cancerous, so it is usually removed surgically early in life. Adrenal gland is not affected and can produce androgens and most of these persons develop pubic hair, though it often remains sparse.
Primary amenorrhoea:As gonads have no hormonal or reproductive potential.
Poorly developed secondary sexual characteristics:Due to underdeveloped gonads
- Sparse pubic hair
- Underdeveloped breasts
- However external female genitalia are normal
Associated tumors:Gonadal dysgenesis with the Y chromosome is found to be associated with the occurrence of the germ cell tumors with a reported incidence of 10–30%
- Gonadoblastoma (M/C) (5–10% cases of Turner syndrome are also associated with gonadoblastoma)
Early diagnosis is important for a number of reasons: firstly, because of the risk of gonadal malignancy; secondly, early institution of hormonal therapy is vital for the induction of puberty; thirdly, HRT is required to prevent osteoporosis.
Differential diagnosis:Other causes of primary amenorrhea due to congenital or structural causes of ovarian insufficiency with female phenotype
- Turner syndrome (M/C)
- Mayer Rokitansky Kuster Hauser (MRKH) syndrome
- Androgen insensitivity syndrome (AIS)
- Swyer syndrome (rarest)
The treatment of Swyer syndrome requires multi-disciplinary teams that are able to provide multi-faceted care in terms of prevention of malignancy and osteoporosis, induction of puberty, fertility, and psychological support.
Prophylactic gonadectomy:A high incidence of tumour such as gonadoblastoma and germ cell malignancies have been reported;