Androgen insensitivity syndrome (AIS) is when a person who is genetically male (who has one X and one Y chromosome) is resistant to male hormones (called androgens). As a result, the person has some or all of the physical traits of a woman, but the genetic makeup of a man.
AIS is caused by genetic defects on the X chromosome. These defects make the body unable to respond to the hormones that produce a male appearance.
The syndrome is divided into two main categories:
In complete AIS, the penis and other male body parts fail to develop. At birth, the child looks like a girl. The complete form of the syndrome occurs in as many as 1 in 20,000 live births.
In partial AIS, people have different numbers of male traits.
Partial AIS can include other disorders, such as:
Infertile male syndrome is also considered to be part of partial AIS.
A person with complete AIS appears to be female but has no uterus. They have very little armpit and pubic hair. At puberty, female sex characteristics (such as breasts) develop. However, the person does not menstruate and become fertile.
People with partial AIS may have both male and female physical characteristics. Many have partial closing of the outer vagina, an enlarged clitoris, and a short vagina.
There may be:
Complete AIS is rarely discovered during childhood. Sometimes, a growth is felt in the abdomen or groin that turns out to be a testicle when it is explored with surgery. Most people with this condition are not diagnosed until they do not get a menstrual period or they have trouble getting pregnant.
Partial AIS is often discovered during childhood because the person may have both male and female physical traits.
Tests used to diagnose this condition may include:
Other blood tests may be done to help tell the difference between AIS and androgen deficiency.
Testicles that are in the wrong place may not be removed until a child finishes growing and goes through puberty. At this time, the testes may be removed because they can develop cancer, just like any undescended testicle.
Estrogen replacement is prescribed after puberty.
Treatment and gender assignment can be a very complex issue, and must be targeted to each individual person.
The outlook for complete AIS is good if the testicle tissue is removed at the right time. The outlook for partial AIS depends on the appearance of the genitals.
Call your health care provider if you or your child has signs or symptoms of the syndrome.
Reviewed By: Anna C. Edens Hurst, MD, MS, Assistant Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.