Swyer syndrome, also called 46, XY complete gonadal dysgenesis, is a disorder that affects a person’s gender (sexual development). Gender is usually determined by the X and the Y chromosomes (sex chromosomes). Males usually have one X and one Y (46, XY) and females usually have two X’s (46, XX). Individuals with Swyer syndrome have the chromosomes of a male (46, XY) but develop female reproductive structures (internal and external female genitalia). Affected individuals will also have underdeveloped ovaries or testes (gonadal dysgenesis). They will instead have clumps of tissue, called streak gonads, which are usually surgically removed because they can become cancerous over time. People with Swyer syndrome cannot reproduce (infertile).
Changes (mutations) in the SRY, MAP3K1, NR5A1, and DHH genes are the cause of some cases of Swyer syndrome. These genes are instructions for the body to make proteins that are important for male sexual differentiation. If a baby has a mutation in one of these genes, the baby will not develop male genitalia, even if they have an X and a Y chromosome. Some cases of Swyer syndrome are caused by exposure to hormonal medication during pregnancy. The cause for most cases is unknown. When Swyer syndrome is caused by a gene mutation, it is usually not inherited from an affected parent, but is instead due to a random new mutation that occurs in the baby.
Swyer syndrome is considered in a baby who has female genitalia with streak gonads. Chromosome testing is usually ordered and shows an X and a Y chromosome. Additional genetic testing can be ordered to confirm the diagnosis. Affected children will need hormone replacement therapy for normal sexual characteristic (breasts and menstruation) development. If your child has been diagnosed with Swyer syndrome, talk to their doctor for a more specific treatment plan. Support groups are available for more information and support.