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Inherited Disorders and Birth Defects

Cystic Hygroma and 45x/46xy: Mosaic Turner`s?

09/24/2007

Question:

During a routine dating ultrasound at 14 weeks pregnancy our baby was diagnosed with a cystic hygroma and we were referred to a genetic councillor. A subsequent ultrasound was done a week later that showed the cystic hygroma may have grown and that there is also an accumulation of some fluid in the baby’s chest.

An amniocentesis has just been completed and the doctor has informed us that the baby has 45x/46xy mosacism, with a higher concentration of 46xy chromosomes. The Doctor has told us this could result in a child being born with Turner Syndrome, a child being born that is intersex, or a normal male child.

What is the likelihood of each of these outcomes, and what additional test can we have done and what additional questions can we ask. Our next ultrasound and appointment is in one week, so any advice you can provide is appreciated!

Answer:

I agree with your doctor - children that have 45,X/46, XY mosaicism can have features ranging from a girl with Turner syndrome, to normal boys - although they usually are infertile, to babies that have ambiguous genitalia (it is not clear looking at the genitals whether or not the child is a boy or girl).

Most often when there is 45,X/46, XY mosaicism found on prenatal diagnosis, if there are no other problems in the fetus, the outcome is a normal male infant. The literature says about 90% of the time.

However, if there are other problems found, in your case that would be the cystic hygroma and fluid accumulating in the chest - then it is very difficult to say what the outcome of the pregnancy will be. Usually in this type of situation, a comprehensive ultrasound looking at all the major organ systems, such as the heart, kidneys, brain, the genitals, is the best way to follow the pregnancy and gives you the most information.

When you return for you ultrasound examination, hopefully you will be discussing the findings with a team of people - your doctor, the specialist doing the ultrasound, the geneticist and/or genetic counselor. They will have the most up-to-date and detailed information.

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Response by:

Anne   Matthews, RN, PhD Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University