fallon

I wonder the samething

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musicmom

Ari2

The possible genetic cause(s) of autism (more properly, "autism spectrum disorders" = ASD) is a hot topic. But it's complicated.

Autism spectrum disorders are classified as "pervasive developmental disorders". Pervasive developmental disorders include 1) autistic disorder (the "classic" Kanner autism), 2) Rett disorder, 3) childhood disintegrative disorder, 4) Aspbergers, 5) and a throw-away, catch-all label of "pervasive developmental disorder - not otherwise specified", which is frequently referred to just as PDD-NOS.

Research so far on ASD and on just autistic disorder suggests possible involvement on several chromosomes, including the X chromosome (which would explain the male predominance of these disorders, with the exception of Rett's) and chromosomes 15-17.

But there's a few problems. First, the concordance rate among identical twins varies by studies but usually is not as high as you would expect for a genetic disorder. This means that unlike other "pure" genetic disorders you don't find the rate among identical twins to be at or near 100%. Instead, with ASD you find more cases than you would expect in which one identical twin has ASD and the other doesn't. Second, the rate of ASD in kids with parents with ASD is lower than you would expect for a genetic disorder.

There is an association with parental age at conception and autism: The older either parent is, the greater the chance the kid will have ASD. This might suggest either spontaneous = new mutations and/or problems with genetic imprinting.

Related to imprinting, what might be involved is something called epigenetics. Epigenetics is a theory that believes environmental factors can cause DNA to behave differently while not changing the actual DNA sequence. So different genes can be turned off or on, but no genetic mutation has occurred. This sort of sounds like what you were getting at Fallon, when you were talking about possible environmental effects without getting into changes to the genetic sequence (and thanks for the compliment).

Hope that makes some sense.

HappyMomma

I just came across this story. I didn't realize there was a current case on this.

WASHINGTON (AP) -- Parents claiming that childhood vaccines cause autism should not be rewarded by the courts when the scientific community has already rejected any link, government lawyers argued Monday on the first day of a hearing in federal court.

Overall, nearly 4,900 families have filed claims with the U.S. Court of Claims alleging that vaccines caused autism and other neurological problems in their children. Lawyers for the families are presenting three different theories of how vaccines caused autism. The theory at issue Monday was whether vaccines containing the preservative thimerosal caused autism.

Lynn Ricciardella, a Justice Department lawyer, said that theory has not moved beyond the realm of speculation. She said that the Institute of Medicine and theCenters for Disease Control and Prevention have rejected any link between thimerosal and autism.

"There is no scientific debate," Ricciardella said. "The debate is over."

Families argue autism-vaccine link in special U.S. court - CNN.com

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musicmom

Couldn't it be argued that something neurologically is not developed enough in a child brain to accept what ever chemical it's taking in? Therefore, the brain counter acts and deforms?
What if a childs brain was developed substatially and THEN given the vaccine? Some of these vaccines can wait.

Kaytee

I don' tknow about the brain formation info, but I have heard that children who are vaxed later (after 6 months or some say after 2 years) have a much less risk of severe reactions

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Ari2

But it is a balancing act.

Some vaccine-preventable diseases (VPDs) most severely effect kids under the age of 2. An example is the rotavirus. Currently, the first dose is given at 2 months, with others at 4 and 6 months. If kids didn't get the vax until after age 2, the biggest danger period from the virus would have passed.

Hib is similar. Currently, Hib mainly affects under-/unvaxed kids and infants too young to be vaxed (the dosing schedule is the same for the rota vax). If the vax were delayed to past 2 years, it would shift the incidence curve to the older kids. As about 5% of HiB cases are fatal and 20% result in permanent damage, this would increase the deaths and long-term harm from Hib (the cases of Hib in the US has dropped 99% since the Hib vax came out in 1990 - obviously, sanitation hasn't improved in this country by the same amount).

Another example is Hep B. Most Hep B infections begin in infancy or early childhood, and Hep B infections at this early time are most likely to become chronic, life-long problems and an increased risk for liver cancer. So waiting may increase the number of kids who become infected with Hep B, go on to develop chronic Hep B (which can be miserable), and then be at risk for cancer.

Also, the majority of vaccine reactions occur in kids over 1 year of age. Is this because the vaxes given (such as MMR)? Maybe. Is it because older kids have a stronger immune system and thus can mount an overly aggressive response at times? Maybe, and because of this later is not always better (for an example look at the problems with contracting chicken pox later in life).

In terms of waiting for brain development, even forgetting the problem of early VPD infection, I don't think there would be an answer as to when to start vaxing later. Studies that I'm aware of haven't shown a benefit to delaying vaxes or separating out the combined vaxes like MMR. Instead, they show no decrease in adverse effects or autism rates.

I agree that the sheer number of vaxes infants get is scary. It scared me when my kids were tiny, especially as they were premature. But the risk of VPDs at a very young age also scared me. The best one can do, I guess, is to do as much peer-reviewed research as one can (and this might not be a lot) and work to find a ped/FP whom you can trust.

Lissa

Ari, what are your feelings on the varicella vax?

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Ari2

I think the CDC's thinking was a bit misguided, but I can see the benefit.

In general, I would rather my kids get varicella naturally at an early age. The natural immunity appears to be much longer-lasting than the vax immunity. Even with boosters, it is unclear whether vaxed people will have lasting immunity into their 30s and beyond. This threatens to push the age of first infection to later in life, when varicella is much more dangerous. Unfortunately, it is hard for most non-vaxers to find a contagious kid, so their children may not get the natural immunity at a young age.

And chicken pox is not a completely harmless disease. In wild-type infections, the kid usually missed 5-6 days of school, which may place a huge burden on working families. Even relatively mild cases can make a kid completely miserable. There is the small chance of serious complications such as bacterial infections, encephalitis, and pneumonia. In the vast majority of vaxed kids, any case of varicella that does occur is very mild, with much less risk of serious complications. Lastly, there are more and more people walking around with compromised immune systems, and varicella is extremely contagious. Decades ago you just didn't have the same number of people on immune-suppressing drugs or out in the community with a weakened immune system. In these folks and in non-immune pregnant women, varicella is a much more serious disease.

Overall, I think the vax's benefit outweighs the risk, so my kids got the vax. But I'm a bit divided and can understand why some parents would rather opt out and other are strong believers in the vax.

Lissa

Thanks Ari!

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