Mixed gonadal dysgenesis (MGD) is one of the most common disorders of sex development (DSD). It is the second most common cause of sex organs that aren’t well formed or clearly male or female.
Gonads are the body’s main sex organs. Gonads form according to a specific chromosomal pattern. Girls are usually born with two X chromosomes (46,XX). Boys are usually born with one X, and one Y chromosome (46,XY).
Because of the chromosome pattern, boys will normally develop gonads called testicles. Girls develop gonads known as ovaries. Babies born with MGD are born with a mixed chromosomal pattern: 45,XO/46,XY.