Expert: Dr. Raed Kanan - 3/1/2007

Question
Hello Dr. Kanan,

I am currently pregnant (11 weeks) with my 3rd child.  With this pregnancy I was offered a prenatal blood test for the Fragile X Syndrome, and I took it.  With my two previous pregnancies I was not offered the test.  I got my results from my OBGYN yesterday and I'm really confused.  My result was 46 repeats.  I understand that 5-45 is considered normal, although I have read that as high as 50 repeats is normal.  My doctor said he is not concerned, but has referred me for genetic counseling anyway.  I do not have a history of any genetic abnormalities in my family.  No Down's, no trisomy 18, no Turner's, no fragile X.  My 2 children (a boy and girl) are perfect--no problems there.  So this leads me to many questions.

1.  What is the risk that the child I'm carrying having Fragile X?

2.  What does the future hold for my daughter's children?  And future generations?

3.  What exactly is the normal range of CGG repeats?

4.  Does the "grey zone" mean I'm a carrier?  Could my daughter or son be one in just one generation?

I am so worried.  I do not have the genetic counseling appointment for another 3 weeks.  I could really use some peace of mind.  Thank you for your time in answering--I REALLY appreciate it!

Answer
Dear Tanya
I know things are confusing but I don't think you have risk at the moment .. read below for details

The grey zone is the most important point about mutations in the fragile X syndrome gene mutations with CGG repeat number in the 'grey zone' is between approximately 40 and 55 repeats)

The gray zone cannot be the cause of clinical problems, and the gene is perfectly functional.

The only risk associated with a gene of CGG repeat number in the grey zone is that it may be unstable from generation to generation and could eventually expand to a full mutation. ( more than 55 repeats for carriers and < 200 for affected)

Therefore, there is a slight risk of fragile X syndrome in distant descendants. The risk for instability of a gene with less than 50 repeats is quite small


I hope this comfort you.... but I still advice you to meet with the genetic counseling Doctor to confirm with him the results :)

Dr. Raed Kanan
http://kanan.co.nr/