Mixed Gonadal Dysgenesis

Also known as: MGD, disorder of sex development, DSD.

What is mixed gonadal dysgenesis?

Sex is determined by the presence in cells of sex chromosomes X and Y. Girls are born with two X (XX) chromosomes while boys have an X and a Y (XY) chromosome. The gonads (ovaries or testicles) develop under the guidance of the sex chromosome patterns. During fetal growth the ovaries produce estrogen which assists the growth of the vagina and uterus. Testicles produce testosterone as well as a substance to stop the formation of female sex organs, that is needed to form male sex organs. 

Mixed gonadal dysgenesis is a sex developmental disorder where the gonads are abnormal from there being some cells with XY chromosomes and some with just a single X, known as chromosome Y mosaicism. This results in a wide range of male/female genitalia that are not typically, or clearly, male or female. Children with this disorder may have one or two gonads which may be undescended and/or not easy to identify as typical testicles.

What causes mixed gonadal dysgenesis?

MGD is a result of a genetic mutation which is not hereditary.

What are the symptoms of mixed gonadal dysgenesis?

Clinical presentation is extremely variable; from external genitalia appearing totally male or completely female or ambiguous, with the baby appearing neither female or male.

What are mixed gonadal dysgenesis care options?

Treatment (hormones or surgery) depends on the clinical presentation of the external genitalia and will follow from a full discussion of options that the Specialist team at Nicklaus Children's Hospital will review with the family.

Reviewed by: Jack Wolfsdorf, MD, FAAP

This page was last updated on: September 16, 2025 12:19 PM