Swyer Syndrome: Causes, Clinical Manifestations and Pregnancy

By (gynecologist), (embryologist) and (invitra staff).
Last Update: 01/20/2020

Swyer syndrome, also known as pure gonadal dysgenesis 46 XY, is a genetic disorder of the sex chromosomes characterized by the absence of correlation between the sexual phenotype and the genotype.

Therefore, people with this disorder have a male karyotype (46, XY), but anatomically there are female characteristics. Specifically, these XY women have sexual organs such as the vagina, uterus, and fallopian tubes, although they do not have ovaries.

Normally, Swyer syndrome is caused by a mutation in the SRY gene, although the exact etiology is unknown.

What is Swyer's Syndrome?

Swyer Syndrome, also called pure gonadal dysgenesis 46 XY, was first described in 1955 by Dr. Swyer.

In general, this genetic alteration is associated with a mutation in the SRY gene (male sex determinant gene), which inhibits the differentiation of embryonic gonads into testes. However, there are mutations in other genes that also cause this syndrome.

Women with Swyer syndrome have XY sex chromosomes instead of XX, although they have a female reproductive anatomy. Therefore, these patients have vaginas, fallopian tubes and hypoplastic uterus.

It should be noted that Swyer syndrome is rare and it occurs in approximately 1 in 80,000 births.


Currently, the exact cause of Swyer syndrome is not known exactly. However, there are numerous studies linking this syndrome to alterations in the genes involved in normal sexual differentiation.

In 15-20% of patients with this syndrome, mutations occur in the SRY gene, which is found on the Y chromosome. This gene is essential for determining the sex of the male and for the masculinization of the external genitals. Therefore, individuals 46, XY with alterations in the SRY gene become considered women, XY.

When an absent SRY gene embryo is fertilized or this gene is altered, the testicles are not formed and as a consequence, the phenotypic sex is female. However, genotypic sex is XY.

Clinical Manifestations

Most women with pure gonadal dysgenesis 46 XY have normal physical characteristics until the onset of puberty. These women have normal external female genitalia, but this is accompanied by delayed pubertal development.

Mainly, the classic symptom for which adolescents see a doctor is due to primary amenorrhea, which means that the first menstruation does not occur.

At this point, it is discovered that these girls lack ovaries and, therefore, sex hormones. In addition, other typical manifestations of Swyer syndrome include the following:

  • Tall stature due to late closing of growth cartilages.
  • Small uterus.
  • Large clitoris.
  • Absence of secondary sexual characteristics, such as breasts, pubic hair, etc.
  • Wide chest.
  • Development of gonadoblastoma, a benign tumor in the gonads.
  • Infertility due to lack of ovaries.

Making an early diagnosis of Swyer syndrome is crucial to prevent gonads from becoming malignant and developing into tumors.

Diagnosis of Swyer syndrome

The diagnosis of Swyer syndrome is made by a detailed medical history and physical examination. In this way, the specialist will be able to determine if the ovaries are not developed, if they are composed of fibrous tissue and if the period is missing.

Other tests that are performed for a correct diagnosis of Swyer syndrome are:

  • Hormonal analysis, as it is related to a decrease in antimullerian hormone and testosterone. In addition, the hormones FSH and LH are elevated.
  • Visual tests such as abdominal pelvic ultrasound to assess the presence or absence of mullerian ducts and locate malformations.
  • Karyotype to see the chromosome endowment.
  • Molecular analysis to determine the presence of mutations in genes.
  • In some cases endoscopy, laparoscopy and gonadal biopsy are necessary.

All these analyses are also carried out on direct relatives to establish whether it is a sporadic or hereditary condition.


Treatment for Swyer syndrome usually involves hormone replacement with estrogen and progesterone at puberty. This homonal treatment, in addition to helping in the development of secondary sexual characteristics, helps prevent the loss of calcium in the bones.

On the other hand, ovaries are usually removed by laparoscopic surgery to prevent the appearance of gonadal tumors.

Most women with this syndrome need psychological assistance to accept their condition.

Swyer Syndrome and Pregnancy: Assisted Reproduction

One of the major drawbacks for women diagnosed with Swyer syndrome is infertility because they do not present ovaries.

However, thanks to advances in reproductive medicine and assisted reproductive techniques, there is now a solution for this type of sterility. Those women who wish to achieve pregnancy will have to resort to in vitro fertilization with egg donation.

These women, unless they have a uterus that is too small, can carry a pregnancy to term without problems. In addition, when using eggs from young donors, the evolutionary pregnancy rate is high.

Assisted procreation, as any other medical treatment, requires that you rely on the professionalism of the doctors and staff of the clinic you choose. Obviously, each clinic is different. Get now your Fertility Report, which will select several clinics for you out of the pool of clinics that meet our strict quality criteria. Moreover, it will offer you a comparison between the fees and conditions each clinic offers in order for you to make a well informed choice.

FAQs from users

Do I need egg donation if I suffer from Swyer syndrome?

By Marta Zermiani M.D., Ph.D. (gynecologist).

Yes. These patients are able to become pregnant because their uterus is normal. However, as they do not have ovaries
eggs can only come from egg donation.
Read more

Can Swyer syndrom be passed onto offspring?

By Marta Barranquero Gómez B.Sc., M.Sc. (embryologist).

In some cases, Swyer's syndrome is not hereditary, but is caused by a genetic mutation that occurs spontaneously, with no known cause.

However, some women have close relatives with the same SRY gene mutation who did not develop the syndrome. In these cases, genetic studies would have to be done to find out if it is an inherited disorder.

Can Swyer syndrome cause cancer?

By Marta Barranquero Gómez B.Sc., M.Sc. (embryologist).

Yes. There's a 40% risk of altered gonads becoming malignant. This can occur in childhood or early adolescence, even before the syndrome is diagnosed.

The most common tumors are gonadoblastoma and dysgerminomas.

How often does Swyer syndrome occur?

By Marta Barranquero Gómez B.Sc., M.Sc. (embryologist).

Approximately 1 in 80,000 births worldwide have Swyer's syndrome. This is why it is considered a rare syndrome.

Suggested for you

We have commented that the main reason why women with Swyer syndrome go to the doctor is the absence of menstruation. If you want more information about it, you can visit the following article: What is amenorrhea?

Patients with Swyer syndrome may get pregnant with egg donation. For more information, click here: Donor-Egg IVF Procedure: Protocol & Cost.

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FAQs from users: 'Do I need egg donation if I suffer from Swyer syndrome?', 'Can Swyer syndrom be passed onto offspring?', 'Can Swyer syndrome cause cancer?' and 'How often does Swyer syndrome occur?'.

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Authors and contributors

 Marta Zermiani
Marta Zermiani
M.D., Ph.D.
Graduated in Medicine and Surgery from the Università degli Studi di Padova in Italy, specializing in Gynecology and Obstetrics at the Hospital Universitario de Bellvitge in Barcelona. Specialist in Assisted Reproduction with 4 years experience and currently a gynecologist at Vida Fertility Madrid. More information about Marta Zermiani
Licence number: 280847526
 Marta Barranquero Gómez
Marta Barranquero Gómez
B.Sc., M.Sc.
Graduated in Biochemistry and Biomedical Sciences by the University of Valencia (UV) and specialized in Assisted Reproduction by the University of Alcalá de Henares (UAH) in collaboration with Ginefiv and in Clinical Genetics by the University of Alcalá de Henares (UAH). More information about Marta Barranquero Gómez
License: 3316-CV
Adapted into english by:
 Romina Packan
Romina Packan
inviTRA Staff
Editor and translator for the English and German edition of inviTRA. More information about Romina Packan

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