Disorders of sex development (DSDs), also known as differences in sex development, diverse sex development and variations in sex characteristics (VSC) are congenital conditions affecting the reproductive system, in which development of chromosomal, gonadal, or anatomical sex is atypical.

DSDs are divided into following categories, emphasizing the karyotype's role in diagnosis:

• 46, XX DSD: mainly virilized females as a result of congenital adrenal hyperplasia (CAH) and girls with aberrant ovarian development.
• 46, XY DSD: patients with abnormal testicular differentiation, defects in testosterone biosynthesis, and impaired testosterone action.
• Sex chromosome DSD: patients with sex chromosome aneuploidy or mosaic sex karyotypes. This includes patients with Turner Syndrome and Klinefelter Syndrome even though they do not generally present with atypical genitals.
• XX, Sex reversal: consist of two groups of patients with male phenotypes, the first with translocated SRY and the second with no SRY gene.
• Ovotesticular disorder: patients having both ovarian and testicular tissue. In some cases the ovarian tissue is functional.
• XY, Sex reversal: patients with female phenotypes where duplication in the Xp21.2 region of the X chromosome that contains the NR0B1 (DAX1) gene is associated with XY sex reversal.

46,XX testicular difference of sex development is a condition in which individuals with two X chromosomes in each cell, the pattern typically found in females, have a male appearance. People with this condition have male external genitalia. They generally have small testes and may also have other features such as undescended testes (cryptorchidism) or the urethra opening on the underside of the penis (hypospadias). A small number of affected people have external genitalia that do not look clearly male or clearly female. Affected children are typically raised as males and develop a male gender identity.

At puberty, most affected individuals require treatment with the male sex hormone testosterone to induce development of male secondary sex characteristics such as facial hair and deepening of the voice (masculinization). Hormone treatment can also help prevent breast enlargement (gynecomastia). Adults with this condition are usually shorter than average for males and are unable to have children (infertile).

Trisomy X, also called triple X syndrome or 47,XXX, is characterized by the presence of an additional X chromosome in each of a female's cells. Although females with this condition may be taller than average, this chromosomal change typically causes no unusual physical features. Most females with trisomy X have normal sexual development and are able to conceive children.

Trisomy X is associated with an increased risk of learning disabilities and delayed development of speech and language skills. Delayed development of motor skills (such as sitting and walking), weak muscle tone (hypotonia), and behavioral and emotional difficulties are also possible, but these characteristics vary widely. Seizures or kidney abnormalities occur in about 10 percent of affected females.

People with 47, XXY have an extra chromosome. The X and Y chromosomes are the sex chromosomes. Females usually have two X chromosomes (46, XX) and males usually have one X and one Y chromosome (46, XY). People with 47, XXY have two X chromosomes and one Y chromosome. Some people with 47, XXY may have no noticeable signs or symptoms (features) or only mild features. Others may have more moderate to severe features. Common symptoms of 47, XXY include low testosterone, infertility, speech and language problems, and learning difficulties. Although the majority of people with 47, XXY identify as males (gender identity), some people with 47, XXY identify as female, intersex, transgender, or prefer not to identify with a gender at all. A diagnosis of 47, XXY may be suspected by signs and symptoms and confirmed by genetic testing. Diagnosis may also be made during prenatal genetic testing or infertility testing.

People with 47, XXY are at an increased risk of developing diabetes, metabolic syndrome, osteoporosis, cardiovascular diseases, autoimmmune disorders, and certain mental health problems. Regular screening for these health problems is suggested. Although most males with 47, XXY are infertile, many produce sperm and may be able to conceive with assisted reproduction. A discussion about testosterone therapy with a pediatric endocrinologist is advised, even if the person with 47, XXY does not identify as male. Other features of 47, XXY may be managed by early intervention, speech therapy, occupational therapy, physical therapy, extra help in school, counseling, and social skills training.

Less commonly, some woman are found to be 47, XXY. In most of these cases, a change or mutation has been found in a gene that helps control male sexual development. Most often, women with 47, XXY are infertile, but in a few cases they have had children naturally.

47,XYY syndrome is characterized by an extra copy of the Y chromosome in each of an individual's cells. Although many people with this condition are taller than average, the chromosomal change sometimes causes no unusual physical features. Most individuals with 47,XYY syndrome have normal production of the male sex hormone testosterone and normal male sexual development, and they are usually able to father children.

47,XYY syndrome is associated with an increased risk of learning disabilities and delayed development of speech and language skills. Affected children can have delayed development of motor skills (such as sitting and walking) or weak muscle tone (hypotonia). Other signs and symptoms of this condition include hand tremors or other involuntary movements (motor tics), seizures, and asthma. Individuals with 47,XYY syndrome have an increased risk of behavioral, social, and emotional difficulties compared with their unaffected peers. These problems include attention-deficit/hyperactivity disorder (ADHD); depression; anxiety; and autism spectrum disorder, which is a group of developmental conditions that affect communication and social interaction.

Physical features related to 47,XYY syndrome can include increased belly fat, a large head (macrocephaly), unusually large teeth (macrodontia), flat feet (pes planus), fifth fingers that curve inward (clinodactyly), widely spaced eyes (ocular hypertelorism), and abnormal side-to-side curvature of the spine (scoliosis). These characteristics vary widely among people with this condition.

49,XXXYY syndrome is a chromosome abnormality that occurs when a male inherits two extra copies of the X chromosome and one extra copy of the Y chromosome. The condition is extremely rare with only a handful of cases reported in the medical literature. Signs and symptoms associated with these cases include severe intellectual disability, distinctive facial features, normal to tall stature, gynecomastia, hypogonadism, and behavioral abnormalities. 49, XXXYY syndrome is likely caused by a mistake (called nondisjunction) that occurs at conception or during the formation of the sperm and/or egg. Treatment is based on the signs and symptoms present in each person.

Aromatase deficiency is a condition characterized by reduced levels of the female sex hormone estrogen and increased levels of the male sex hormone testosterone.

Females with aromatase deficiency have a typical female chromosome pattern (46,XX) but are born with external genitalia that do not appear clearly female or male. These individuals typically have normal internal reproductive organs, but develop ovarian cysts early in childhood, which impair the release of egg cells from the ovaries (ovulation). In adolescence, most affected females do not develop secondary sexual characteristics, such as breast growth and menstrual periods. They tend to develop acne and excessive body hair growth (hirsutism).

Men with this condition have a typical male chromosome pattern (46,XY) and are born with male external genitalia. Some men with this condition have decreased sex drive, abnormal sperm production, or testes that are small or undescended (cryptorchidism).

There are other features associated with aromatase deficiency that can affect both males and females. Affected individuals are abnormally tall because of excessive growth of long bones in the arms and legs. The abnormal bone growth results in slowed mineralization of bones (delayed bone age) and thinning of the bones (osteoporosis), which can lead to bone fractures with little trauma. In affected individuals, the body does not respond correctly to the hormone insulin, so people with aromatase deficiency can have abnormally high blood sugar (glucose), a condition known as hyperglycemia. In addition, people with armoatase deficiency can have excessive weight gain and a fatty liver.

Women who are pregnant with fetuses that have aromatase deficiency often experience mild symptoms of the disorder even though they themselves do not have the disorder. These women may develop hirsutism, acne, an enlarged clitoris (clitoromegaly), and a deep voice. These features can appear as early as 12 weeks of pregnancy and go away soon after delivery.

Denys-Drash syndrome is a condition that affects the kidneys and genitalia.

Denys-Drash syndrome is characterized by kidney disease that begins within the first few months of life. Affected individuals have a condition called diffuse glomerulosclerosis, in which scar tissue forms throughout glomeruli, which are the tiny blood vessels in the kidneys that filter waste from blood. In people with Denys-Drash syndrome, this condition often leads to kidney failure in childhood. People with Denys-Drash syndrome have an estimated 90 percent chance of developing a rare form of kidney cancer known as Wilms tumor. Affected individuals may develop multiple tumors in one or both kidneys.

Although males with Denys-Drash syndrome have the typical male chromosome pattern (46,XY), they have gonadal dysgenesis, in which external genitalia do not look clearly male or clearly female or the genitalia appear female-typical. The testes of affected males are undescended, which means they are abnormally located in the pelvis, abdomen, or groin. As a result, males with Denys-Drash are typically unable to have biological children (infertile).

Affected females usually have normal genitalia and have only the kidney features of the condition. Because they do not have all the features of the condition, females are usually given the diagnosis of isolated nephrotic syndrome.

Exstrophy-epispadias complex (EEC) refers to a spectrum of birth defects that includes epispadias, classical bladder exstrophy, and exstrophy of the cloaca and several variants. EEC is characterized by a visible defect of the lower abdominal wall and other problems. In normal development, the cloacal membrane temporarily separates the cloaca (final part of the intestine) into urogenital and anal regions, and it ruptures after fusing with a structure known as the urogenital septum, which is made up of the tissue that will form the abdominal muscles (mesoderm). If the cloacal membrane does not fuse correctly with the urogenital septum, it does not form the mesoderm and, as a result, the abdominal muscles do not form. The exact timing of the rupture determines whether the child is born with isolated epispadias, classic bladder exstrophy, or cloacal exstrophy. Depending on severity, EEC may involve the urinary system, musculoskeletal system, pelvis, pelvic floor, abdominal wall, genitalia, and sometimes the spine and anus.

There is no known cause for EEC. Treatment may involve several surgeries to repair the abdominal wall and any associated malformations.

Frasier syndrome is a condition that affects the kidneys and genitalia.

Frasier syndrome is characterized by kidney disease that begins in early childhood. Affected individuals have a condition called focal segmental glomerulosclerosis, in which scar tissue forms in some glomeruli, which are the tiny blood vessels in the kidneys that filter waste from blood. In people with Frasier syndrome, this condition often leads to kidney failure by adolescence.

Although males with Frasier syndrome have the typical male chromosome pattern (46,XY), they have gonadal dysgenesis, in which external genitalia do not look clearly male or clearly female or the genitalia appear female-typical. The internal reproductive organs (gonads) are typically undeveloped and referred to as streak gonads. These abnormal gonads are nonfunctional and often become cancerous, so they are usually removed surgically early in life.

Affected females usually have normal genitalia and gonads and have only the kidney features of the condition. Because they do not have all the features of the condition, females are usually given the diagnosis of isolated nephrotic syndrome.

Hypospadias (pronounced hype-oh-spay-dee-us) is a birth defect in boys where the opening of the urethra (the tube that carries urine from the bladder to the outside of the body) is not located at the tip of the penis.

In boys with hypospadias, the urethra forms abnormally during weeks 8–14 of pregnancy. The abnormal opening can form anywhere from just below the end of the penis to the scrotum. There are different degrees of hypospadias; some can be minor and some more severe.

Klinefelter syndrome (KS) is a condition that occurs in males when they have an extra X chromosome. Some males with KS have no obvious signs or symptoms while others may have varying degrees of cognitive, social, behavioral, and learning difficulties. Adults with Klinefelter syndrome may also have primary hypogonadism (decreased testosterone production), small and/or undescendent testes (cryptorchidism), enlarged breast tissue (gynecomastia), tall stature, and/or inability to have biological children (infertility), as well as an abnormal opening of the penis (hypospadias), and an small penis (micropenis). KS is not inherited, but usually occurs as a random event during the formation of reproductive cells (eggs and sperm) that results in the presence of one extra copy of the X chromosome in each cell (47,XXY). KS treatment is based on the signs and symptoms present in each person. Life expectancy is usually normal and many people with KS have normal life. There is a very small risk of developing breast cancer and other conditions such as a chronic inflammatory disease called systemic lupus erythematosus.

In some cases, there is more than one X chromosome in each cell (for example, 48,XXXY or 49,XXXXY). These conditions, which are often called "variants of Klinefelter" syndrome usually have more serious problems (intellectual disability, skeletal problems, and poor coordination) than classic Klinefelter syndrome (47,XXY).

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is a disorder that mainly affects the female reproductive system. This condition causes the vagina and uterus to be underdeveloped or absent, although external genitalia are normal. Affected individuals usually do not have menstrual periods due to the absence of a uterus. Often, the first noticeable sign of MRKH syndrome is that menstruation does not begin by age 16 (primary amenorrhea). People with MRKH syndrome have a female chromosome pattern (46,XX) and normally functioning ovaries. They also have normal breast and pubic hair development. Although people with this condition are usually unable to carry a pregnancy, they may be able to have children through assisted reproduction.

When only reproductive organs are affected, the condition is classified as MRKH syndrome type 1. Some individuals with MRKH syndrome also have abnormalities in other parts of the body; in these cases, the condition is classified as MRKH syndrome type 2. In this form of the condition, the kidneys may be abnormally formed or positioned, or one kidney may fail to develop (unilateral renal agenesis). Affected individuals commonly develop skeletal abnormalities, particularly of the spinal bones (vertebrae). People with MRKH syndrome type 2 may also have hearing loss or heart defects.

Perrault syndrome is a rare condition that causes different patterns of signs and symptoms in affected males and females. A key feature of this condition is hearing loss, which occurs in both males and females. Affected females also have abnormalities of the ovaries. Neurological problems occur in some affected males and females.

In Perrault syndrome, the problems with hearing are caused by changes in the inner ear, which is known as sensorineural hearing loss. The impairment usually affects both ears and can be present at birth or begin in early childhood. Unless hearing is completely impaired at birth, the hearing problems worsen over time.

Females with Perrault syndrome have abnormal or missing ovaries (ovarian dysgenesis), although their external genitalia are normal. Severely affected girls do not begin menstruation by age 16 (primary amenorrhea), and most never have a menstrual period. Less severely affected women have an early loss of ovarian function (primary ovarian insufficiency); their menstrual periods begin in adolescence, but they become less frequent and eventually stop before age 40. Women with Perrault syndrome may have difficulty conceiving or be unable to have biological children (infertile).

Neurological problems in individuals with Perrault syndrome can include intellectual disability, difficulty with balance and coordinating movements (ataxia), and loss of sensation and weakness in the limbs (peripheral neuropathy). However, not everyone with this condition has neurological problems.

Swyer syndrome is a genetic condition affecting sexual organ development, classified as a disorder of sex development (DSD). In Swyer syndrome, people with one X chromosome and one Y chromosome, normally present in males, are born with female external genitalia and underdeveloped gonads (ovaries or testes) known as streak gonads. Most people with Swyer syndrome are raised as females. Adolescents with this condition do not go through normal puberty and are infertile.

Some cases of Swyer syndrome are caused by genetic alterations (mutations) in one of several genes, but in some cases the cause is unknown. The inheritance pattern depends on the responsible gene. This condition is diagnosed based on the chromosome results, clinical examination, and imaging studies.

Treatment includes removal of streak gonads to prevent cancer and hormone replacement therapy from puberty onward. While women with Swyer syndrome are infertile, they may become pregnant with the use of donated eggs.

Turner syndrome is a chromosomal condition that affects development in people who are assigned female at birth. Females typically have two X chromosomes, but in individuals with Turner syndrome, one copy of the X chromosome is missing or altered.

The most common feature of Turner syndrome is short stature, which becomes evident by about age 5. Reduced functioning of the ovaries, the female reproductive organs that produce egg cells (oocytes) and female sex hormones, is also very common. The ovaries develop normally at first, but egg cells usually die prematurely and most ovarian tissue breaks down before birth.

Many affected individuals do not undergo puberty unless they receive hormone therapy, and most are unable to become pregnant naturally. A small percentage of people with Turner syndrome retain normal ovarian function through young adulthood.

About 30 percent of individuals with Turner syndrome have extra folds of skin on the neck (webbed neck), a low hairline at the back of the neck, puffiness or swelling (lymphedema) of the hands and feet, skeletal abnormalities, or kidney problems. One-third to one-half of individuals with Turner syndrome are born with a heart defect, such as a narrowing of the large artery that leaves the heart (coarctation of the aorta) or abnormalities of the valve that connects the aorta to the heart (the aortic valve). Complications associated with these heart defects can be life-threatening.

Most people with Turner syndrome have normal intelligence. Developmental delays, nonverbal learning disabilities, and behavioral problems are possible, although these characteristics vary among affected individuals.