What is it?

Swyer syndrome is a rare congenital disorder of sex development. It is characterized by the failed development of the sex glands.

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Signs & symptoms

Humans with Swyer syndrome develop with external phenotypes typical of females and nonfunctional gonads instead of ovaries or testes. Individuals are most commonly diagnosed during puberty after menstruation fails to occur (primary amenorrhea).
The consequences of Swyer syndrome without treatment:
* Gonads do not have two X chromosomes, so the breasts will not develop and the uterus will not grow and menstruate until estrogen is administered. This is often given transdermally.
* Gonads cannot make progesterone, so menstrual periods will not be predictable until progestin is administered, usually as a pill.
* Gonads cannot produce eggs, so conceiving children is not possible without embryo transfer. There has been a case of unassisted pregnancy in one woman with XY gonadal dysgenesis, who had a predominantly 46,XY karyotype- a 46,XY karyotype in peripheral lymphocytes, mosaicism in cultured skin fibroblasts (80% 46,XY and 20% 45,X), and a predominantly 46,XY karyotype in the ovary (93% 46,XY and 6% 45,X)0 who gave birth to a 46,XY female with complete gonadal dysgenesis.
* Streak gonads with Y chromosome-containing cells have a high likelihood of developing cancer, especially gonadoblastoma. Streak gonads are usually removed within a year or so of diagnosis, since the cancer can begin during infancy.
Osteopenia is often present.


Although affected individuals are born with Swyer syndrome, diagnosis rarely occurs at birth. Most cases of this syndrome are diagnosed in their teens, when tested for delayed puberty and amenorrhea. The diagnosis of Swyer syndrome is made based upon a thorough medical history, clinical evaluation, identification of characteristic findings, and a variety of tests.
An individual’s physical appearance may also lend to a particular diagnosis. A differentiating feature of individuals with Swyer syndrome is their increased height during puberty and their lack of secondary XX-related characteristics, such as menstrual cycles, enlarged breasts, as well as pubic and axillary hair.
Oftentimes, imaging is suggested in order to identify the internal genital organs of the reproductive system. Initially, an ultrasound is usually performed. Magnetic resonance imaging (MRI) can also be performed if the ultrasound findings are concerning or unclear. For further investigation, diagnostic laparoscopy can be performed, which is a minimally invasive surgical procedure that provides a clear view of the abdominal organs through a few small incisions.
Chromosomal analysis is often mandatory in order to confirm diagnosis of Swyer syndrome. A specific procedure that requires the identification of each chromosome, called fluorescent in situ hybridization, (FISH) can be used to determine their 46XY karyotype, that visually represents the human’s chromosomal makeup. Additional genetic analysis may be performed in order to identify the specific gene mutations associated with Swyer syndrome.


The treatment of Swyer syndrome primarily focuses on managing associated characteristics of the condition through hormone therapy. Additionally, preventive measures may also be taken in order to prevent the development of cancer.
Swyer syndrome is treated with hormonal replacement therapy, including the replacement of estrogen and progesterone, the two main hormones that are produced by the ovaries. When possible, this therapy usually begins at the ages associated with puberty, specifically during adolescence in order to induce menstruation and the development of secondary XX-related characteristics, such as breast enlargement, and body hair. Hormone replacement therapy can also help prevent bone loss and thinning (i.e. osteoporosis) later during life, as estrogens play an important role in the growth and maturation of the bones.
In order to mitigate the risk of cancer, streak gonads are often removed surgically to avoid a gonadal malignancy.

☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.

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