All you need to know about: Swyer Syndrome

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Swyer syndrome itself cannot currently be reversed, but its effects can be managed |Image used for representational purpose only | Photo Credit: AP

Swyer syndrome is a rare condition in which a person is born with XY chromosomes, the combination usually associated with males, but their reproductive organs develop along a typically female pattern. The person typically has female external anatomy and a uterus and fallopian tubes.

The condition often goes unnoticed during childhood and comes to light during adolescence, when puberty does not progress normally or menstruation does not begin. It can also be diagnosed later during investigations for infertility. Here’s all you need to know about Swyer syndrome.

Swyer syndrome is a rare difference of sex development, medically known as 46,XY complete gonadal dysgenesis. According to the US’ Genetic and Rare Diseases Information Center, a person with the condition has a 46,XY chromosome pattern, but the gonads do not develop into functioning testes. Instead, they remain as small, non-functioning structures called “streak gonads”. The person generally develops female external genitalia, while the uterus and fallopian tubes are usually present. The condition is estimated to occur in about one in 80,000 people,

Swyer syndrome results from disruption of the genetic pathway involved in testicular development during early embryonic development. The SRY gene, located on the Y chromosome, plays an important role in initiating this process. However, an SRY mutation is not found in every person with Swyer syndrome.

Swyer syndrome may not be apparent during childhood and often comes to light during adolescence, when puberty does not progress normally. One of the most characteristic signs is primary amenorrhoea, meaning that menstruation does not begin.

Delayed or incomplete development of secondary sexual characteristics can also prompt investigation. Because the streak gonads do not produce sufficient sex hormones, spontaneous breast development may be limited. The condition can sometimes remain undiagnosed even when a person reaches adulthood.

Diagnosis usually involves looking at the person’s chromosomes, hormone levels and reproductive anatomy. Karyotyping, a test that examines the number and structure of chromosomes, typically shows a 46,XY pattern in Swyer syndrome. Blood tests generally show evidence of gonadal failure, including low levels of sex hormones and elevated levels of hormones such as follicle-stimulating hormone and luteinising hormone. Ultrasound or MRI can be used to examine the uterus and the gonads.

Genetic testing can be used to investigate the underlying cause, including variants in SRY and other genes involved in gonadal development. However, not finding an SRY mutation does not exclude Swyer syndrome. In some patients, even more extensive genetic testing may not identify the precise molecular cause.

There is currently no treatment that can change the 46,XY chromosome pattern or turn the streak gonads into functioning ovaries. However, the effects of Swyer syndrome can be effectively managed. Hormone replacement therapy, usually involving oestrogen and subsequently an appropriate progestogen regimen when indicated, is used to induce and maintain puberty, support development of secondary sexual characteristics and protect bone health.

The streak gonads also need to be assessed because they carry an increased risk of gonadoblastoma, a type of germ-cell tumour. Decisions about gonadectomy and its timing are now generally individualised according to the underlying diagnosis and tumour risk.

Fertility is another important consideration. Because the streak gonads cannot produce eggs, people with Swyer syndrome cannot conceive using their own eggs. However, if the uterus is present and sufficiently developed, pregnancy can be possible through IVF using a donated egg or embryo. Research shows that patients with Swyer syndrome can have successful pregnancies following endometrial preparation with hormones and IVF using donated eggs. Following pregnancy and delivery, continued hormone replacement is important for maintaining bone health.

In other words, Swyer syndrome itself cannot currently be reversed, but its effects can be managed. Hormone replacement can address the absence of normal gonadal hormones, removal of the streak gonads can reduce the risk of tumours, and assisted reproductive techniques can make pregnancy possible for some patients.

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