46XX

46,XX is a human chromosomal constitution in which there are 46 chromosomes, including two X chromosomes. It is the most common karyotype associated with the genetic sex female. In individuals with 46,XX, gonadal development typically leads to ovaries and a female internal reproductive tract, and most have typical female secondary sexual characteristics and fertility depending on other factors.

Most 46,XX individuals develop normally as females, with ovaries, a uterus, fallopian tubes, and female-typical external genitalia. However, a minority have conditions affecting sex development (disorders of sex development, DSD) that can alter phenotype or reproductive anatomy. One well-known example is congenital adrenal hyperplasia (CAH), where androgen excess during fetal development can lead to virilization of the external genitalia in 46,XX individuals, while internal female structures generally remain present.

Other 46,XX-related DSDs include 46,XX testicular DSD and ovotesticular DSD. In 46,XX testicular DSD, the SRY gene or related sex-determining factors are present on an X chromosome or an autosome, causing testicular development in a genetically female karyotype; individuals are typically raised as males and have testes but often limited fertility. Ovotesticular DSD (ovotestis) involves both ovarian and testicular tissue and can present with a range of genital phenotypes, from typically female to ambiguous to male.

Less common is 46,XX gonadal dysgenesis, in which ovarian development is impaired, leading to primary amenorrhea and underdeveloped secondary sex characteristics. Diagnosis relies on karyotyping, hormonal assessment, and imaging, with management tailored to the specific condition and the individual’s gender identity and reproductive goals.