Wednesday, 23 July 2014

Autism and developmental delay in our genetic makeup

Ever since my son was diagnosed with Autism and Developmental delay you can't help but wonder if it was something I did that was bad, and if the rumours about thing such as vaccinations were true.  Maybe there's something wrong with my genetic makeup, or my husband's.  Maybe

I saw the paediatrician and she recommended we do some blood tests which I was rather ambivalent about. I wasn't particularly thrilled about taking him for blood tests but I did them eventually with the help of EMLA that I pinched from work, and he was brilliant and didn't even flinch when they took his blood, much to my relief.  The usual blood workup for autism was done which included a whole bunch of metabolic tests, endocrine tests (including thyroid function) and general bloods as well as some genetic stuff.

Yesterday my paediatrician called to discuss the results, and she told me that there were some abnormalities in his chromosome microarray, which is a test looking at his DNA to see if there were any deletions or duplications.  And they found that he had a "heterozygous duplication within chromosome band 15q13.3 which involves only one gene CHRNA7".

The report stated that a large study had found that this particular duplication is associated with ADHD (Attention Deficit Hyperactivity Disorder) though my son doesn't have that, but another study said that duplications in the 15q11-13 segments were associated with autism, especially if the duplications were on the maternal side of the chromosome.

Even more concerning to me is when I read all things like this:
The recurrent 15q13.3 microdeletion/microduplication has been reported to cause mental impairment, autism spectrum disorder, facial dysmorphism, seizures and epilepsy...Some of the common clinical features of the BP4a - BP5 ~500 kb deletion were speech delay, developmental delay, ADHD, aggressive behavior, ADHD, and hearing loss. None of the three deletion cases were reported to have either seizures or epilepsy. Phenotypic features of individuals with the ~500 kb duplication include growth delay, midface hypoplasia, speech delay, mild autism and one case exhibiting seizures. Further studies are needed to determine whether CHRNA7 duplications are more likely polymorphic variants with little clinical significance or possibly causative with incomplete penetrance and/or variable expressivity. These results suggest that the deletion/duplication of the CHRNA7 gene by itself may not be sufficient by itself to cause seizures and epilepsy, and may instead be a susceptibility gene related to speech delay, ADHD, autism and aggressive behavior.
There's even a pamphlet on that particular gene duplication!

Looking at that, what does that really mean?  I know that genetic things have incomplete penetrance, so people having this gene don't necessarily get autism, but it makes me wonder for the future - is my son going to pass autism down to his children? If I had known I had a defective gene would that affect my decision to have children even though the chance of anything happening is small?

I find it remarkable that genes are like computer programs or files. The files can copy incorrectly, have errors, have recurring segments or deletions - and in a computer program or file it may have no impact at all, or it may have a massive impact.  I feel lucky that the impact on my son seems small - looking around at other children who have duplications in those regions, they could have ended up with major developmental abnormalities, retardation and poor physical development.

So what does it mean in the present moment?

It means I need to go speak to a geneticist to figure out if I need to do any further tests on my son, or even myself and my husband to see if this thing has any relevance. If either he or I have the same duplication then perhaps it's just an incidental finding that isn't associated with anything as neither of us have autism or developmental delay (that I know of!).  But obviously there is no treatment (nor would I seek one) because my son is going along just fine at the moment.  Makes me wonder in the future when he's grown up and his partner wants to have children, what would they think of this? Though if my son grows up and has no impairments or disability then it would probably not mean anything and he could go on living a normal productive life.  Which is all a mother could hope and dream for!

1 comment:

  1. Hi, on Facebook there are a few groups that discuss 15q13.3 duplications. There are people with alot of knowledge that are more than happy to share it :) My little one has the exact same duplication, he is going a lot better than anyone could have imagined. Wishing you and your family all the best ♡