Disorders of sex development, or DSD, refer to atypical development of any of the 5 steps of sex differentiation described previously. Sometimes, DSDs are evident at birth. Sometimes DSDs are not identified until later in development. Some, but not all, of the medical conditions that are classified under the larger category of DSD are listed below:


 

Hypospadias

is among the most common birth defect observed in boys. Hypospadias occurs when the opening of the urethra, referred to as the urinary meatus, opens along the underside of the penis rather than at the tip.

Congenital Adrenal Hyperplasia

(CAH) affects approximately 1 in 15,000 children and affects both boys and girls. People with CAH are unable to produce sufficient amounts of the hormones cortisol and aldosterone. As a result, adrenal androgens are over-secreted. The excess production of androgens associated with CAH leads to genital masculinization in affected girls.

Turner Syndrome

(TS) affects approximately 1 in 2500 girls. Girls with TS usually possess one X chromosome (45,XO) while unaffected girls usually possess two X chromosomes (46,XX). TS is associated with ovarian dysgenesis, and as a result of this dysgenesis affected girls typically do not menstruate or become pregnant.

Klinefelter Syndrome

(KS) is the most common sex chromosome disorder and it affects approximately 1 in 1000 boys. Boys with KS usually possess two X chromosomes (47,XXY) while unaffected boys usually possess one X chromosome (46,XY). KS is associated with decreased testosterone and sperm production.

Micropenis

refers to a very small penis with a normal urinary opening at the tip and two descended testicles in a normal scrotum.

Vaginal Agenesis/Meyer-Rokitansky-Küster-Hauser Syndrome

(MRKH) affects approximately 1 in 5000 girls. MRKH refers to the congenital absence of a uterus and varying degrees of atypical development of the cervix and vagina.

Gonadal Dysgenesis

refers to atypical development of ovaries or testes from a common gonadal precursor during fetal development.

Androgen Insensitivity Syndrome

(AIS) occurs when cells of the body are unable to respond to androgens. Two forms of AIS exist, the complete form (CAIS) and the partial form (PAIS).

5-α-Reductase Deficiency

is a condition where the body is unable to produce dihydrotestosterone (DHT), the most potent form of androgen. In boys, DHT is required for genital masculinization during fetal development.

Bladder Exstrophy

affects approximately 1 in 40,000 children. This condition is due to failure of the abdominal wall to close during fetal development, resulting in abnormal development of the bladder and external genitalia.

Cloacal Exstrophy

affects approximately 1 in 250,000 children. Like bladder exstrophy, the bladder and external genitalia are affected. Unlike bladder exstrophy, the large intestines are also affected in people with cloacal exstrophy.