XY gonadal dysgenesis

XY complete gonadal dysgenesis, also known as Swyer syndrome, is a condition in which an individual with a 46,XY karyotype has a female phenotype. Those affected typically have normal vulvas but underdeveloped gonads, described as fibrous streak gonads, and without hormone replacement therapy they typically do not experience puberty. The cause is often, but not always, inactivation of the SRY gene, which is responsible for sexual differentiation. Pregnancy is sometimes possible with assisted reproductive technology and, in at least one reported case, without it. The syndrome is named after Gerald Swyer, an endocrinologist at University College Hospital in London, who first reported two cases in 1955.