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Fragile X Syndrome

(46 Posts)
JAKEJEM Tue 20-Sep-05 21:32:01

Some of you probably remember me posting on here before about my DS who is now 3 and has been provisonally diagnosed with autism. We are now awaiting a multi-disciplary panel for a final assessment. Whilst waiting, it has come to light that our son may have Fragile X Syndrome. He certainly has ALL the characteristics and our GP/HV/SALT & Portage worker agree. He has his blood tests on Monday and I wonder if anyone else knows anything about this and how long the blood tests take to work etc. Would be grateful for any replies. Thanks once again. Nikki.

Lillypond Tue 20-Sep-05 21:37:50

I've no advice, but we are taking DS tomorrow for his blood tests for Frangile X and Fish test. I'll be interested to read what other people know about this.

Good luck with the results.

Jimjams Tue 20-Sep-05 21:38:23

Frag X is one of the most common genetic causes for autism. There are 2 tests they can do- one looks at the chromosomes in their entirity and takes a while, and one looks for a genetic marker- and is faster (and more accurate). All children with autism in our HA get tested for Frag X- I had to chase our results up though (ds1 doesn't have it).

I did meet someone once who had a son initially dxed with autism, then Frag X- she said as soon as she got the dx all this help materialised out of the ether. Her son's needs hadn't changed, but his dx had- and wow he got help! So she was quite pleased.

Check when the blood tests are done- and then ring when they are expected in.

JAKEJEM Tue 20-Sep-05 21:42:14

Thanks Lillypond/JimJams - Good luck for tomorrow Lillypond, how is your DS with having his bloods taken - we are really dreading it, I am getting worked up already and we still have 6 days to wait! Do you think your son shows any signs - and what is the FISH test?

Jimjams Tue 20-Sep-05 21:45:32

The FISH test is the specific test for the marker. It's more accurate.

Jimjams Tue 20-Sep-05 21:47:44

oh hang on that's wrong-there is another purely molecular test they can do. I;'m confused as to which we had done now. FISH is pretty accurate though.

Lillypond Tue 20-Sep-05 21:49:56

Thanks Jakejem - Our paed. doesn't think DS has Fragile X as he doesn't show any of the characteristics, but as Jimjams said, all children with an autism DX are tested in our area. I have no idea what a FISH test is. I didn't know he was going to have one but it came with the wallet for the Fragile X test.

DS has never had a blood test before so I don't know how he will react. I hate them so will have to look away. DP is coming as well just incase he needs both of us to hold him still

JAKEJEM Tue 20-Sep-05 21:52:54

We have been told that we are having the FMR1 test for Fragile X which is the more accurate DNA test (99%) rather than the chromosone one. Just looked up the FISH test and it says this is for testing Williams syndrome?

Jimjams Tue 20-Sep-05 21:53:10

A FISH test just labels the chromosomes fluorescently. So if your child has a marker for Frag X you'll get a fluorescent label on your X chromosome. And the chromosomes will glow....

Jimjams Tue 20-Sep-05 21:54:44

You can get FISH tests for all sorts of things- it describes the technique rather than the test.

Ahh we had that molecular one as well. That's good - not everywhere does it AFAIK (they may do now but I was advised to ask for it)- it's all coming back....

Lillypond Tue 20-Sep-05 21:57:20

Oh I've confused myself here. Sorry jakejem.

I've just looked at DS's paperwork and he's not having a FISH test. He's just being tested for Fragile X.

Thanks for the info Jimjams.

Jimjams Tue 20-Sep-05 21:58:54

He may still be having FISH though lilypond- just for FragX (or he may be having the molecular test)

Good luck with it all xxx

tamum Tue 20-Sep-05 22:02:09

I can't actually see how FISH would test for Fragile X to be honest- it's a trinucleotide repeat expansion, so even if you could use it you would miss out on all the information on repeat length. I've certainly never come across it being used, but maybe I've missed something that Jimjams knows. The most direct test is to look at the FMR1 gene, as you've said. Good luck with the tests

Lillypond Tue 20-Sep-05 22:05:29

Oh bloody hell. I should have paid more attention in biology lessons . I never thought I'd be discussing chromosones and cytogenetics outside of the science lab.

I don't think it's FISH as they have ticked 'routine chromosones' and left FISH blank. Maybe the paed. didn't think it necessary as she doesn't think he has it.

tamum Tue 20-Sep-05 22:09:49

It does all get a bit surreal on here at times, Lilypond

bluebear Tue 20-Sep-05 22:15:42

Def. can't test for fragile X using the FISH technique - the current method of testing is the molecular test for FMR1 (as tamum said).
Usually all the chromosomes are looked at as well (as Jimjams said) in a seperate test (karyotype) in case something else (not fragile X) is causing the features.

FISH is a method used to look for very small rearrangements (usually tiny missing bits) of chromosomes when there is a specific syndrome suspected (like Williams syndrome)

Jimjams Tue 20-Sep-05 22:16:54

No you're right. I think pre 90's it used to be tested for cytogentically (??) but not sure how. I think I was thinking of a piccy in one of my books showing the Frag X site cytogentically and for some reason I remembered it as FISH (black and white photo). Buggered if I can find the book now though so can't check.

I know the mother I spoke to made a big thing about making sure that we had the molecular test as her son had been given a cytogentic test and had been missed- then re-tested a few years later using the molecular test and picked up. Ds1 was about 2 then though, so 2001 and her son was 9 or 10ish IIRC - so I guess that makes sense.

Jimjams Tue 20-Sep-05 22:18:56

useful link

tamum Tue 20-Sep-05 22:19:21

That's right Jimjams, but it was tested for by looking for a folate sensitive fragile site, so specific culture conditions. I wouldn't have thought there was any real reason to that rather than test the gene directly nowadays (guess what I was lecturing on today, eh?)

JAKEJEM Tue 20-Sep-05 22:21:19

Does anyone have any personal knowledge of Fragile X? Have read all the books etc and DS matches, just wondered if he is a "textbook" case?

Jimjams Tue 20-Sep-05 22:28:01

no- I just meant the mother I spoke to woulddn't have had the option of anything other than cytogentic testing initially which must have been why she went on about it to me iyswim.

Found the book! Yep it mentions the folate-sensitive site and then describes it as "overambitious" to expect such a simple test to pick up the variants.

Two piccies- one solid stained- and one G-banded. TBH i don't see how anyone can see a thing on the G banded slides (baaaad memories ) PLeased I wasn't imagining the book/pics but god knows why I had it tagged FISH in my memory.

I'm meant to know about multivariate repeats as well. (or at least I was meant to- maybe I did once).

bluebear Tue 20-Sep-05 22:28:23

Well since it's you Jimjams - here comes the science bit

The 'fragile' site at the end of the X chromosome is caused by the expansion of a trinucleotide repeat sequence...when the number of repeats gets very high the area becomes unstable and if you culture white blood cells in media which is low in folate some of the X chromosomes will express the repeat sequence as a 'fragile site' which looks like a break in the chromosome. We used to diagnose fragile X this way until about 6 years you know it was not completely accurate as not all samples would express the fragile site. And it couldn't detect carriers.
The molecular tests can look for the number of repeats at the gene locus and also find out if the gene is methylated or not. (It is methylated in affected people - so therefore 'switched off') Which is much more accurate and can detect carriers.

(Hope I got that right, I helped a little with the hand over from cytogenetics to molecular in this region but it was all a long time ago)

Wish I could tell you how long the tests will take JakeJem but it varies so much from region to region.

Jimjams Tue 20-Sep-05 22:29:28

JAKEJEM _ i wish I could pass you onto the mum who spoke to me- but I no longer have her email address. Perhaps there is a yahoo groups site you could join for Frag X? Often someone is happy to answer questions.

bluebear Tue 20-Sep-05 22:30:38

I am such a slooooooww poster

Jimjams - the G banding swells the chromosomes so it's harder to see then. We screened on solid stained to identify the fragile sites, then de-stained and banded the cell to check the breakpoint.

Jimjams Tue 20-Sep-05 22:31:29

Well tthat's completely embarrassing as I was meant to look at microsatellites Although it was over 10 years ago! And a disaster so I concentrated on cytogenetics (not that well obviously )

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