Androgen insensitivity syndrome (AIS) is a condition that affects development of the reproductive and genital organs.
Dr Trisha Macnair last medically reviewed this article in November 2010.
Androgen insensitivity syndrome
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What causes it?
AIS is a genetic disorder caused by a mutation in the androgen receptor gene, which leaves the body insensitive to the male sex hormones or androgens. This abnormal gene is found on the X-chromosome and is thought to occur in about one in every 20,000 births.
What are the symptoms?
People with AIS are genetically male, as they have XY chromosomes. Normally, androgen hormone stimulates the development of male characteristics, but in AIS the body doesn't respond as usual to the hormone because of the abnormal gene.
Some people are totally insensitive to the effects of androgen and develop external genitalia that are female in appearance. This is known as complete androgen insensitivity syndrome (CAIS).
Others have varying degrees of sensitivity to androgen, called partial androgen insensitivity syndrome (PAIS), which results in external genitalia development that ranges from completely male to completely female, or somewhere in between.
People born with complete AIS are not usually identified until puberty, when pubic hair doesn't grow and periods fail to start. Although the child appears female and may have external female genitalia , there are no internal female genitalia (no fallopian tubes, uterus or upper two-thirds of the vagina) because the development of these is blocked by the testes which usually remain inside the body, where they produce the male hormone testosterone.
During childhood, a girl may be found to have bilateral inguinal hernias, often containing the testes. Meanwhile in those children male external genitalia, many of the changes expected at puberty such as a change in voice or the development of facial hair or acne, don’t occur.
What's the treatment?
There's no cure, although medical treatments and surgery may help a person to function in the gender they feel most comfortable with.
The most important part of managing AIS is the explanation and counselling given to parents and the child concerned. An expert psychologist should be involved.
The problem can be compounded by not being diagnosed at birth.
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