Here is a description of several DSD (disorders of sex development). In the descriptions, “gonad” means either testes, ovaries, or a structure which have aspects of each.
AIS: Androgen Insensitivity Syndrome (AIS) occurs when an individual has one X and one Y chromosome, but the body is unable to respond to androgens (male sex hormones). During prenatal development, an individual with complete AIS (CAIS) will develop female external genitalia, while a person with partial AIS (PAIS) may have external genitalia that appear mainly female, or mainly male, or anything in between. Because the testes function normally, uterus and fallopian tubes do not develop. Vagina may be of any length, from short to entirely normal. Pubertal development includes feminine appearance of breasts and hip shape. There are neither eggs nor sperm. Stature is often quite tall. In PAIS, there is an increased risk of cancer developing in the testes, so surgical removal is commonly recommended. The risk of cancer development in CAIS is much lower.
46, XY gonadal dysgenesis: 46, XY gonadal dysgenesis (Swyer’s syndrome) occurs when an individual has one X and one Y chromosome, but the testes do not develop normally. During prenatal development, an individual with this condition will develop a uterus and female external genitalia. However, the internal genitalia are fibrous “streaks”, neither testis nor ovary. Hormone supplementation is required to promote development at puberty. There are neither eggs nor sperm. Stature is often quite tall. In 46, XY gonadal dysgenesis, there is an increased risk of cancer developing in the streak gonads, so surgical removal is commonly recommended.
Gonadal dysgenesis/ Mixed gonadal dysgenesis: In partial gonadal dysgenesis, the testes function, but not at the same level as typical testes, resulting in ambiguous genitalia at birth. In mixed gonadal dysgenesis, a streak gonad develops on one side, and a partially developed testis on the other side. As the internal gonads in both of these conditions are more prone to develop cancer, surgical removal is usually recommended. Hormone supplementation is then required to promote development at puberty. Chromosomal pattern is often mixed, with any combination of 46, XX, 46, XY, and 45, X patterns.
5-alpha reductase deficiency: This is one of several conditions where an individual has one X and one Y chromosome (the usual male pattern), but the genitalia at birth do not look like a classical boy. The condition is characterized by an absence of the enzyme 5-alpha reductase, which converts testosterone to the hormone dihydrotestosterone (DHT). Without DHT, prenatal genital development results in a generally female appearance. Because masculine puberty depends more strongly on testosterone than on DHT, puberty will be virilizing (unless the gonads are removed or a blocking medication is used). It is not uncommon for individuals with this condition to transition to a male gender role at puberty. Sperm can develop. Stature is similar to other males in the family.
17-beta-hydroxysteroid dehydrogenase deficiency: Individuals with this disorder have an XY chromosome pattern, but have a genetic defect in the function of the enzyme 17-beta-hydroxysteroid dehydrogenase, which is in the synthetic pathway in which testosterone is produced. At birth, these individuals can have either ambiguous external genitalia or complete female external genitalia. These children are generally raised as female, and their diagnosis is often discovered when there is absence of menstruation, or when they begin to masculinize during puberty (slowly become more like a man; deepening of the voice, acne, male musculature etc). Neither uterus nor sperm are produced normally. Testes are often surgically removed at the time of puberty to prevent further masculinization, and to prevent any chance of cancer in the testes.
Ovotesticular DSD: In typical sex development, the fetus develops two tiny organs called “proto-gonads” (which sort of means “starter gonads”). In typical males, those proto-gonads become testes, whereas in females, those proto-gonads become ovaries. In some circumstances the proto-gonad may become an ovotestis, which means it contains some cellular elements of ovaries as well as some cellular elements of testes. Although a person may be born with two ovotestes, it is much more common for a person to be born with a normal ovary on one side but an ovotestis on the other, or one testicle with an ovotestis on the other side. Some people with ovotestes look fairly female-typical at birth, some look fairly male-typical, and some look more in-between (they have “ambiguous genitalia”). Many different chromosomal and anatomical combinations have been observed in people with ovotestes. So diagnosis of ovotestes will not reveal the sex chromosomes, genetic composition, or internal anatomy of a patient. Other tests are required to determine those elements. The testicular portion of ovotestes increases the risk of cancer. For this reason, when ovotestes are diagnosed, usually the testicular portion is surgically removed. In a patient who identifies as a boy or man, the ovarian tissue may also be removed.
MRKH Syndrome (formally known as Mayer-Rokitansky-Kustner-Hauser Syndrome): These young women have a 46, XX chromosomes, and ovaries develop normally. However, the internal female structures do not develop in the typical fashion. A girl born with MRKH may be missing part or all of the vagina, the uterus, and the Fallopian tubes. MRKH Syndrome sometimes also involves unusual development of the skeleton, internal ears, and in rarer cases, the heart, fingers and toes.
Sex differentiation (becoming male or female) is a multi-step process. There are key "branch points" during embryonic and fetal life that shapes a baby's chemistry and anatomy. Here is a link from AboutKidsHealth, Hospita for Sick Children in Toronto, Ontario, Canada that explains more.
You may also find descriptions of common DSD on ISNA's website:
(Click here for a photo gallery of many wonderful women with DSDs.)