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Why do chromosome deletions/bits missing happen? Maybe too big a question but need to put my mind at rest

(26 Posts)
used2bthin Thu 08-Sep-11 20:35:19

Or not of course! I took chinese herbs from an alternative therapist before I knew I was pregnant and also anti biotics which I was told to stop when I found out I was pregnant. Also drank a lot. We are talking about the two-three weeks before I found out but I do worry.

DD has a genetic condition which I know is becase XP and I both carry the faulty gene for an she had a one in 4 chance of being affected. So that I know is just how it is, nothing to do with anything i did or didnt do.

Now she is having various tests as she has severe language impairment/specific learning difficulties. She possibly/probably has epilepsy and has microcephaly (small head). She has just been found to have a small bit missing from chromosome four which the geneticist said only one person on the database shares. The geneticist says all the things above could be linked to the chromosome thing-they may not be but could be. Except the original diagnosis of the genetic cpndition which is completely separate.

So he chromosome 4 bit, is this genetic like the other one, just inherited or can what happens in pregnancy affect chromosomes? I guess it can in some chromosome issues?

Tota1Xaos Thu 08-Sep-11 20:46:00

I'm not a scientist, but as I understand it, the chromosome issue is due to what happens at the sperm/egg stage, in terms of cell copying, so whatever you did in early PG is irrelevant, so please don't blame yourself. I think the chromosome issues may be inherited (if you or x had the same missing bit) or then again may not.

used2bthin Thu 08-Sep-11 21:01:08

Thank you. I think the geneticist is half expecting me or XP to carry the same deletion as the other child on the database has a parent who passed it on but is healthy themselves.

I just have been thinking that if it is a chomosome thing then it definately can't be something I did then it occured to me that maybe it was a pregnancy thing.

Bit disappoitnig to only have one person with it as it doesnt tell us much for the future.

spiritsam Thu 08-Sep-11 21:05:16

I just got told by Paed today DD has deletion of chromosome 22 we have referral to geneticist , sorry can't be more help but just wanted to let you know someone is in the same boat x

2011RWC Thu 08-Sep-11 21:07:34

As Tota1 said what happened during your pregnancy was irrelevant. Inherited Genetic faults can travel hidden through the generations for years depending on the type, where the fault lies, who marries who, whether boys or girls are born and so on. Your eggs will already have formed when you were a fetus inside your mums tum!
DeNovo means new, not present before - in genetics not transmitted or possessed by parents. Its such a complicated field - which I suppose it why only smart people work in it but please don't blame yourself, genetic conditions are so down to chance and just shitty bad luck sad

used2bthin Thu 08-Sep-11 21:11:41

Hi spiritsam thanks. And hope this thread didn't alarm you. I think it is probably the case that it is just one of those things.

Our geneticist is lovely btw and has been really thorough and willing to answer questions. I just hadn't asked this one as it only just occured to me!

thing is all this new stuff about dd doesn't change the facts-that she is way behind but making slow progress.

used2bthin Thu 08-Sep-11 21:14:59

2011RWC x posted,thank youbthat is really reassuring. i am sensitive today, dd was hark work for her new school and I have been wondering if they think her issues are bad parenting-think I am a bit paranoid!

So chromosome issues=genetic? I know that sounds dim but I wasn't sure!

spiritsam Thu 08-Sep-11 21:39:47

Hi used
No not alarmed at all . My DD is making slow progress too . Did you have to wait long to see Geneticist ?
How old is your DD and what problems does she have if you don't mind me asking ? x

cheesetoastie Thu 08-Sep-11 21:45:44

Very small deletions can be inherited in the same way that 'faulty genes' are inherited (in fact some faulty genes are due to very very tiny deletions within the gene). Some genes you need two working copies of, some you only need one working copy so you can have a gene missing and not be affected but if that chromosome is inherited by a child and from their other parent they inherit another non-working copy of the gene then they will have no working copies. And just to make it more complicated sometimes the effect of a missing gene depends on what other genes you have so in one person there may be no affect whilst someone else might be badly affected.
Non-inherited deletions tend to occur when the egg/sperm cells are being made. The DNA has to be copied so the chromosomes double up and then are pulled apart into two cells. The mechanism which copies the DNA can slip when making the new copy and miss a bit - this means that the new copy has a deletion. In women the cells that become egg cells go through this process (first stage of meiosis) when the woman themselves are a fetus, by the time you are born your egg cells have already gone through this stage and are waiting for the next stage. So it's highly unlikely that anything you've taken in pregnancy has caused the deletion.

cheesetoastie Thu 08-Sep-11 21:47:35

Heck I type slowly! - What 2011RWC said!

used2bthin Thu 08-Sep-11 21:49:32

not at all, dd is nearly five and we saw a geneticist within a few weeks of asking but we were already under her since dd was diagnosed with her other condition at birth.

Developmentally dd's understanding of language is around a two and a half year old or was last year when she was assessed-so rougky half her age. Her speech is extremely unclear and at the same assessment was put at a 20month old so her speech and language are really badly affected but she does talk and signs a bit, she is talking more and more in fact which is encouraging. She has delay in her fine motor skills and has really poor attention span. She also obsesses over things and more recently her behaviour has got very tricky.

Did they say how long you'd have to wait for the geneticist? We are waiting for an MRI for her possible epilepsy and to see about the small head size and that has been a long wait but we have recently seen a neurologist which I fond reassuring as he seemed very relaxed about it all!

used2bthin Thu 08-Sep-11 21:52:58

Ah thanks cheesetoastie and that makes sense-it sounds similar to when dd was diagnosed with the genetic disorder-xp and I both have a gene deletion bt have a healthy copy too so are unaffected-dd was affected due to getting both our deletions.

So, we need to see what the results of mine and xps blood tests come back with this time. I am so reassured that it couldnt have been anything I did- I have had this niggling worry over it.

tabulahrasa Thu 08-Sep-11 22:32:32

My science is fairly rusty, but I'm fairly sure you're looking at things like radiation to alter chromosomes

lisad123 Thu 08-Sep-11 22:52:43

We are having tests in next week!
I will say this, some genes can change later in life. Dh cancer is because two of them swapped places, but also due to treatment he now has an extra 8th cromosone.

dolfrog Thu 08-Sep-11 23:39:45

you find this Wikipedia article useful Introduction to genetics which includes a table of links to more complex issues as well.

Grey24 Thu 08-Sep-11 23:40:39

My DH is an academic/researching geneticist, I will ask him tomorrow if he can add to this info at all. He's really good at explaining stuff & being v well read in current research etc. Will ask him & post back if anything useful to you. Our DD has language/speech delay.

messmonster Fri 09-Sep-11 00:37:01

My DD age 3 has a very rare chromo disorder called supernumerary ring chromo 9 whereby she has an extra bit of chromo 9 in a ring shape. She also has it in mosaic form which means some cells in her body have normal DNA and other cells have this extra bit of chromo 9 - with me so far?? smile

Anyway, what I really wanted to say is that by far the best source of information on chromosome disorders is a charity called Unique and their website is here

Their Yellow Book explains a lot about how these things happen. They also have a database (worldwide) which contains the details of other children and families who have registered with them with the whole range of chromo disorders, including I'm sure deletions on 4.

When my DD was diagnosed at 2 weeks, they were by far the best source of info and support for us (and we had a lovely geneticist btw, he just had never come a across a case like my DD) and through them we've met the only other family in the UK with the same condition as my DD.

FWIW OP from the reading I've done I agree with all the others that there's absolutely no connection with what happened before you knew you were pg.

HTH

used2bthin Sat 10-Sep-11 17:43:51

Thanks everyone you have put my mind at rest. I have spent so long worrying about how DD got her SLI.

Grey24 that would be great if he would, the geneticist said that it is more about the future now and for any future siblings or children of dd because there is only the one other child with the same deletion. Its on the opposite bit of chromo four to the bit affected with WolfHirshprung disease if that makes sense.

lisad good luck with yours. I think I read somewhere that you can have changes and DD's microcephaly seems to have happened later on or at least no one picked up on it earlier, very strange esp as she seemed to develope normally until around age one.

messmonster thanks I have spoken with unique and they were nsure as to whether they could help yet as I didn't know which bit of the chromosome at that stage. They also said maybe wait as the geneticist did say it is such a small peice missing she wants to test me and XP before deciding how relevant it is. However the other child with the same bit missing has developmental delay and the child's mother who is completely healthy and NT has the same bit missing so it could be something which is passed on but doesn't always affect people. She seemd to think it could be the cause of dd's issues though or at least she thought it possible.

Will have a look at that link now Dolfrog thanks.

Herecomestheninkynonk Sun 11-Sep-11 16:34:13

Hi used2bthin (me also!)

My DS has a unique microdeletion and I went through thoughts just like you. I mistook an implantation bleed as a period and went on holiday upset about not being pregnant, drank lots, ate all the things you shouldn't etc, etc.

In my case we know the the missing genes are from me although mine are "normal", so have been told countless times it was not my fault, it was a faulty egg. Nothing could have changed that. Sometimes I'm okay with that, sometimes I still feel I am responsible for making my child's life so difficult and I worry about his future constantly.

I have also been told that even if you have two children with an identical genetic abnormality they can be affected totally differently. Not much help I know, but it means you have to go on your child's strengths and weaknesses only, getting help with whatever their specific needs are.

Somehow we have to get past the "how did this happen?" question, but it's hard. At least lots of people on here to share with and provide support x

kimt83 Sun 11-Sep-11 17:54:20

havent read all the replies (have heache and cant concerntrate on them) so might be repeating someone
but
sometimes deletions just happen. its bit like a spelling mistake. sometimes not all of the information is copied over. its how my genetics consultant explained how i am the first person in my family to have the genetic condition i have without either of my parents carrying it ;)

used2bthin Sun 11-Sep-11 19:45:41

Thanks herecomesthe ninkynonk and kimt83.

Yes I think I have to somehow come around to the idea that even with a cause like this there isn't any real explanation. She will have an MRI in october but I suspect it will just show what we know-her speech and language function is impaired as is memory.

Herecomestheninkynonk me too- I thought I was on my period and put in a tampon and carried on as normal, it was christmas so I was out nearly evey night and being 26 and a bit of a heavy drinker at the time that meant a lot of drinking and also ate all the stuff I shouldn't and saw the chinese herbalist to cure my digestive problems (what a waste of money as I had to stop taking them as soon as I found out I was pg and eventually had to bin them-especially funny given that my digestive problems probably werent being helped by the large amounts of booze and rich foods!) Also though, I mistook implantation pains for a pelvic infection (so did the GP) so had anti biotics too.

2011RWC Sun 11-Sep-11 19:59:25

Used2 I meant to say I still have many moments of what ifs....I ran a marathon while pregnant, exercised too much, DH takes tablets for an existing condition and the advice about coming off them while trying is hazy (from 3 months to 1 year) we opted for about 4 as we were desperate to start trying! It can be torturous sad but the sensible side has to keep saying nope it was just how it was meant to be!

used2bthin Mon 12-Sep-11 15:28:31

Its hard not to get caught up in the guilt thing isn't it? Agree about sensible side. I think half my problem is being knackered all the time it makes me paranoid and anxious! Just got in from hospital dd had a fit this morning. Exhausted as she barely slep last night!

SWANUK Mon 03-Oct-11 20:14:01

Hi all, my name is lauren and i am the project coordinator for SWAN UK which is a support project for families with children with undiagnosed genetic conditions / who are going through the process of diagnosis. If you would like to be able to chat to other families in similar situations to you and access information about genetics please do come and find us on facebook under SWANchildrenUK or check out our blog www.swanuk.wordpress.com. You can also contact me directly on SWAN@geneticalliance.org.uk or 0207 7043141.

You can also find accessible information and support about rare chromosome conditions from UNIQUE, the rare chromosome disorder support group, www.rarechromo.org

take care, lauren

glimmer Tue 04-Oct-11 17:54:05

I think the deletions we are talking about here are so rare, that nobody has done statistics on them. However, some more common genetic disorders, eg. Down Syndrome are linked to the age of the egg. So possibly your age is a factor.

Some micro-deletions are considered 'nonclinical familial variants' , while others
are clinical and linked to learning disabilities. Often geneticists like to test the parents and if they have the same deletions but no symptoms, they are considered 'normal variants'.

Most of the time the deletions are sporadic (i.e. random as function of maternal age) and not inherited - so there nothing you did. What put my mind at ease was that there are so many women drinking and running in pregnancy, but they have children without genetic problems. If there would be a link,
doctors would know by now.

A mosaic (where the disorder is not in all cells) form is almost always sporadic and not inherited: At some point there was a copying error and it got copied from then on.

For most disorders the learning disabilities range from mild to severe. So often this info is not a lot of help. In any case you tend to be alone out there, because you will have to address the specific issues of your DC. However, sometimes it can help, e.g. to diagnose potential related problems, like kidney malfunction of hearing problems and/or weight gain issues.

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