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Babies with androgen insensitivity syndrome (AIS) will have XY (usual male pattern) chromosomes. Their external genitals will either appear as female or have an appearance that is not usual for a boy or girl.

There are 2 main types of AIS, which affect people in different ways:

• complete androgen insensitivity (CAIS)
• partial androgen insensitivity (PAIS)

CAIS is not usually obvious from birth because affected babies have female genitals, including a vagina and labia (folds of skin either side of the vaginal opening).

They'll also have undescended testicles, but this will usually go unnoticed unless they cause a hernia (where they push through a weakness in the surrounding tissue).

The first signs usually begin at puberty, which starts at around the age of 11 or 12.

When a girl with CAIS reaches puberty, she will:

• develop breasts and have growth spurts as normal, although she may end up slightly taller than usual for a girl
• not start having periods
• develop little or no pubic and underarm hair

Girls with CAIS do not have a womb or ovaries, so are unable to get pregnant. Their vagina will also be shorter than normal, which may make some sexual acts difficult.

The development of children with PAIS can vary.

In many cases, the genitalia at birth is the first sign and affected babies may have:

• an enlarged clitoris (the sexual organ that allows women to have an orgasm)
• partially undescended testicles
• hypospadias – where the hole through which urine passes out of the body is on the underside of the penis, rather than at the end

Children with PAIS are often raised as boys, although they will continue to have a small penis and may develop some breast tissue at puberty.

Some children with PAIS are raised as girls.

Like those with CAIS, people with PAIS do not have a womb or ovaries and will be infertile.