- Congenital adrenal hyperplasia, in which overproduction of hormones in the adrenal gland causes masculinization of the genitals in female infants;
- 5-alpha-reductase deficiency, in which low levels of an enzyme, 5-alpha-reductase, cause incomplete masculinization of the genitals in male infants
- Partial androgen insensitivity, in which cells do not respond normally to testosterone and related hormones, causing incomplete masculinization of the genitals in male infants
- Penile agenesis, in which male infants are born without a penis
- Complete androgen insensitivity, in which cells do not respond at all to testosterone and related hormones, causing female-appearing genitals in infants with male chromosomes
- Klinefelter syndrome, in which male infants are born with an extra X (female) chromosome, which typically causes incomplete masculinization and other anomalies
- Turner syndrome, in which female infants are born with one, rather than two, X (female) chromosomes, causing developmental anomalies
- Vaginal agenesis, in which female infants are born without a vagina
