Swyer Syndrome

Definition - What does Swyer Syndrome mean?

Swyer syndrome is a condition in which a person with a chromosomal makeup of a male, i.e. one X and Y chromosome, has an outward appearance of a female. A person with this disorder develops as a normal female. However, her gonads (or sex glands) are not well developed. This means those affected are infertile but may get pregnant with a donated egg or embryo. Swyer syndrome is a very rare condition, affecting 1 in 80,000 people.

Swyer syndrome is also called XY gonadal dysgenesis.

FertilitySmarts explains Swyer Syndrome

What causes Swyer syndrome? While the exact cause is not known, mutations (or changes) of a gene or genes that take part in normal sex development of a fetus with an XY chromosomal makeup, cause Swyer syndrome. The most important of these genes is the SRY gene, which is the sex-determining region of the Y chromosome. Thus, Swyer syndrome is classified as a sexual developmental disorder.

A person with Swyer syndrome has a female body, female gender identity, but lacks well-developed ovaries, which are replaced by either streak (or remnants of) ovaries or testes. Because ovaries produce the sex hormones, primarily estrogen that is responsible for the development of breasts, these are poorly developed. Afected girls never enter into puberty and never have periods. However, female reproductive organs like uterus and fallopian tubes are present. Since the ovaries produce eggs, these women lack the potential to get pregnant. The residual gonads are at increased risk of becoming cancerous.

In girls suspected of having Swyer syndrome as based on a general examination (sex characteristics, weight, height), a doctor orders hormonal blood tests, such as estrogen and androgen levels and gonadotropin (the hormones guiding the function of gonads) concentrations. Genetic testing is used to confirm the diagnosis of Swyer syndrome, which shows an XY karyotype (or chromosomal makeup) with the normal 46 number of chromosomes.

Hormone replacement therapy (HRT) is vital for stimulating puberty and for preventing bone loss and thinning due to estrogen deficiency. Owing to their cancerous potential, streak gonads are removed through surgery. Following HRT, the woman with Swyer syndrome can conceive using donated eggs.

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