Diagnosing androgen insensitivity syndrome

Androgen insensitivity syndrome (AIS) is sometimes diagnosed soon after a baby is born, although often it's not noticed until a child reaches puberty.

Doctors may suspect AIS based on a child's appearance and sexual development, but some tests will be needed to confirm the diagnosis.

Appearance and sexual development

Partial androgen insensitivity syndrome (PAIS) is usually spotted soon after birth because the genitals have an unusual appearance.

Complete androgen insensitivity syndrome (CAIS) isn't usually diagnosed at birth because the genitals look normal for a girl, although the condition may be picked up if the child develops a Hernia, femoral .

Hernias are where an internal part of the body pushes through a weakness in the surrounding tissue. They can occur in babies with CAIS as a result of the testicles failing to move from the tummy into the scrotum.

When the baby has an operation to repair the hernia, the surgeon may find the testicles inside the hernia or in the tummy, and tests may be arranged to check for CAIS.

If ababy with CAIS doesn't develop a hernia, the condition may go undiagnosed until puberty , whenshe doesn't start having periods and doesn't develop pubic and underarm hair.

Children with AIS often have female genitals, but nofemale internal reproductive organs.

Ifa surgeon thinks they've found testicles ina baby'stummy during a hernia repair operation, a small tissue sample (biopsy) may betaken and analysedto confirm they are testicles and not ovaries.

Testing family members and unborn babies

If someone in your familyhas AIS and the specific genetic fault causing it has been identified, it may be possible to have a blood test to check if you carry the samefault and are at risk of passing it on to any children you have.

Testing can also be carried out in unborn babies whenthere's a known family history of AIS.

There are two main tests that can be carried out during pregnancy to determine whether a baby has the condition:

• chorionic villus sampling (CVS) a sample ofcells are removed from theafterbirth (placenta)for testing, usually with a needle; thisis usually carried out between the 11th and 14th weeks of pregnancy
• amniocentesis a needle isused to extract a sample ofthe fluid surrounding the baby, calledamniotic fluid,for testing; thisis usually carried out between the 15th and 20th weeks of pregnancy

It can be difficult to decide whether or notto have these tests, so it's a good idea to speak toa genetic counsellor first. It's also important to be aware CVS and amniocentesis are estimated to carry around a 1 in 100 chance of causing a miscarriage .